Imma's new book and exhibition are a testament to what the museum has achieved in a short time, writes Aidan Dunne.

It's appropriate that virtually the first words in Imma's new publication, The Collection, pays credit to "all those private and corporate collectors . . . who have generously gifted or loaned artworks to the collection". Imma was established in 1991 after prolonged lobbying.

In other words, it arrived late in the game as regards its prospects for building a collection of modern art, especially without the benefit of very deep pockets. Even within a local context, the prospect of acquiring a representative collection of modern Irish art was forbidding. Prices had risen slowly but immeasurably in the preceding couple of decades.

That is why the role of benefactors was crucial from and indeed prior to the beginning. Long before Imma had opened its new glass doors, the late Gordon Lambert had indicated his intention of donating his formidable collection to the institution, and to establish a trust for future acquisitions. The arrangement was formalised in 1992. It was a huge boon to the fledgling museum.

Visit the current exhibition Eye of the Storm, drawn from the museum's collection, or flick through the handsome new colour book that features a good representative selection of it in large-format colour illustrations, and you will see immediately how important Lambert's contribution has been, and will continue to be.

This is particularly so because he was an assiduous collector over a period of decades, acquiring important works that would not otherwise be available to the museum.

He is the most prominent though by no means the only example. Imma director Enrique Juncosa also highlights the importance of the scheme which allows donations of heritage items to be set against tax. It's obvious that Imma has benefited significantly from this scheme. Noel and Anne Marie Smyth's donation of some 125 works from the McClelland Collection of 20th-century Irish art, notably strong on Northern Irish artists and the work of Tony O'Malley, is a recent, important example.

The final room in Eye of the Storm contains two huge paintings by Sean Scully, both of which found their way to the museum via the same Section 1003 of Taxes Consolidation Act, 1997. Wall of Light (Yellow), with its monumental blocks of simmering colour, is a tremendous work and a great asset to the collection. It is particularly good, though, that the other painting, the beautifully sombre Dorothy, commemorates the late Dorothy Walker, who campaigned tirelessly for the establishment of Imma, served on its board and was interim director prior to the appointment of Declan McGonagle.

Imma is not really in a position to buy substantial pieces by Scully without the existence of such schemes, Juncosa points out. The same applies to Hughie O'Donoghue, several of whose works are in the collection on the same basis.

There is a strong argument that the museum should have several pieces by each of these and indeed several other artists, because of the combination of their profiles abroad and their strong identification with Ireland.

These twinned factors mean that visitors will come expecting to see their work in Imma: a reasonable expectation of a national collection.

The same could be said of James Coleman, one of the best known Irish artists abroad though a virtual unknown in his own country beyond the confines of the art world, partly because, it must be said, his work can reasonably be described as difficult.

Last year Imma managed to win funding from the Heritage Fund to acquire a trilogy of projected slide works by Coleman from the early 1990s. These three pieces are, Juncosa says, "generally regarded as his most important work to date and have been responsible for the establishment of his wide international reputation." Coleman subsequently gave another of his pieces, from the 1970s, to the museum. Together with Strongbow an installation purchased in 1991, it all makes up a substantial body of his work.

Noting the acquisition of Louis le Brocquy's Táin tapestries under Section 1003, Juncosa points out that, despite this welcome addition, le Brocquy still represents one of many gaps in the collection. In a sense, Juncosa brings an outsider's eye to the local scene, and one might expect him to be sanguine about the feasibility of making good such gaps as they apply to 20th-century Irish art.

However, while he is strongly focused on the international dimension of Imma, he has also addressed its domestic duties with great energy and clarity of vision. He is surprisingly forthright about his views on the institution's responsibility when it comes to the question of building and displaying a representative collection of modern Irish art and developing a canonical collection of modern and post-modernist work.

"In my opinion," he writes, "Imma should become the main national repository of modern Irish art, and gaps such as these should be filled as a priority." He also recognises the limitations on space that make exhibition of the collection difficult.

While committed to regular, rotating displays, and to travelling exhibitions that will promote Imma's (and indeed Ireland's) profile, he acknowledges the need for a more substantial structural initiative. Which is where the development of another building, adjacent to the Royal Hospital's formal gardens, comes in. It's a daunting project, but in the long term it is a vital one, important for the institution, for the city and for the country as a whole.

The exhibition takes its title from a recently acquired Michael Craig-Martin painting that makes an excellent cover for the new book on the collection. As a painter, one could say, he is a great graphic designer. In fact, he is foremost a conceptual artist, and as well known for his role in shaping the groundbreaking generation of Young British Artists as for his own, substantial work.

The inclusion of an early film by Craig-Martin, a remarkable document of the West of Ireland in the early 1960s, together with Eye of the Storm from 2003, provides one good indication of the current scope of Imma's collection.

Making your way through the exhibition, which is appropriately divided into two sections, broadly mid-20th century, starting with Jack B Yeats and Mainie Jellett, and contemporary, concluding with those fine Scullys and a terrific installation by Daphne Wright, gives you a sense of just how far Imma has come since 1991.

The same holds for the new book. Broadly speaking, the collection could be said to have reached critical mass, to have become something considerable in its own right, something to be reckoned with, a significant national resource that will generate its own cultural reverberations.

This is not to say that it is anything like homogeneous or complete. It cannot and should not be homogeneous, rather it has to take the form of an ongoing debate, even an argument. The important thing is that different voices are represented in this argument. You won't like everything you see if you visit the museum, nor should you. But over time your mind may be changed by something you see and do not initially like. And, of course, almost by definition, a collection can never be complete.

Eye of the Storm continues at Imma. Irish Museum of Modern Art: The Collection, which provides a lavishly illustrated overview of the collection, costs €45