The event in the northern Adriatic resort pooled six heads of state, two ministers, a state secretary and two ambassadors.
The declaration welcomed the intensifying of regional dialogue in Southeastern Europe at the highest level, noting that it had created a new atmosphere of good neighbourly relations and joint projects in different areas.
"We share the vision of a united Europe as a goal and destiny of all Southeastern European countries. We shall do our best to make that happen," it is noted in the document.
Participants in the meeting described cultural diversity as a distinctive factor in Europe.
"Our readiness to promote inter-cultural and interreligious dialogue, which we pledged at the Tirana forum in 2004, is firm evidence of our determination to respect European standards," reads the declaration.
The document also highlights the need to respect a number of international documents relating to the protection of cultural heritage and underlines the fact that communication is crucial for building a Europe without divisions.
Countries in the region will continue to work towards that aim following a dozen principles cited in the declaration which cover different areas, from the promotion of sustainable cultural and nature tourism to the repossession of cultural artefacts by their countries of origin and the establishment of cooperation promoting dialogue and knowledge of other peoples and their culture, tradition and language.
Participants in the Opatija summit welcomed the adoption of the Varna strategy for the identification, preservation and promotion of cultural corridors in Southeastern Europe and called on countries in the region to adopt it and agree on an action plan.
The Opatija summit was the fourth in a row, after Ohrid, Tirana and Varna. Participants agreed in the closing declaration that the next summit should be held in Sibiu, Romania, in the first half of 2007.