Attracting thousands of journalists and television crews, the summit should provide Wales with a unique opportunity to showcase what its public representatives call "Europe's youngest capital". Labour MEP Wayne David, whose south Wales constituency covers the city and who, with Wales's four other MEPs has been canvassing for months for Cardiff, welcomed the coup.
"This will provide a huge boost for the city ... The summit will effectively put Wales on the European map and allow Cardiff to promote itself as a true European city".
Six thousand delegates and journalists are expected to attend the summit. But Cardiff is also seen as a shrewd political choice which might boost the Conservative vote in what is a traditional Labour stronghold. Edinburgh was the venue for the last EU summit in Britain in 1992, so supporters have been lobbying on the basis that it is now "Wales's turn". Cardiff's bid certainly benefited from the Welsh influence in Brus- sels, where a strong regional identity has begun to emerge.
The "Taffia" could eventually become as effective as the "Murphia", the influential Irish lobby in Europe, on which Welsh political and business leaders increasingly model themselves. Wales is well placed to take advantage of the EU's emphasis on protecting minority languages and cultures, and many Welsh nationalists see efforts to promote a "Europe of the regions" as a chance to challenge the centralists in London.
Devolutionists in both Wales and Scotland are increasingly taking what they call the "Westminster by-pass" to set up their own missions in Brussels.
The Wales European Centre in Brussels groups bodies such as the Welsh Development Authority, local authorities, universities and the Welsh Tourist Board in an unofficial Welsh "embassy" helping the nation to "punch above its weight".
Activity has intensified since the Euro-sceptic former secretary of state for Wales John Redwood was replaced by the more pro-European William Hague, and the centre now rivals Scotland Europa, which lobbies on behalf of local government, business and industry north of the border.
Three Welsh members also sit on the EU's Committee of the Regions, set up under the Maastricht treaty as a forum where regions such as Scotland, Wales and the German Lander can be consulted directly. Taffia-watchers date the real boost in the Welsh EU presence, however, from the arrival in Brussels of the former labour leader Neil Kinnock.
Since his appointment to one of Britain's two seats at the European Commission table in 1995, the former Labour leader has raised the profile and awareness in European circles of Wales as a separate entity within the United Kingdom. Mr Kinnock's wife, Glenys, is a high-profile member of the European Parliament and the pair have emerged as Brussels's "golden couple". BBC Wales has its own full-time correspondent based in Brussels, a move which has helped to highlight "regional" concerns and linkages. The appointment, yet to be matched by Scotland, illustrates the country's growing self-confidence in Europe.