Before their accession to the EU, 9 out of 10 of the applicant countries held referendums (not Cyprus):
| Czech Republic | Referendum15/16 June 2003, 77% voted "Yes" |
| Cyprus | Parliamentary ratification after the signature of the Accession Act |
| Estonia | Referendum 14 September 2003, 66.9% voted "Yes" |
| Hungary | Referendum 12 April 2003, 84% voted "Yes" |
| Latvia | Referendum 20 September 2003, 67% voted "Yes" |
| Lithuania | Referendum 11 May 2003, 90% voted "Yes" |
| Malta | Referendum 8 March 2003, 53% voted "Yes" |
| Poland | Referendum 7-8 June 2003, 77.5% voted "Yes" |
| Slovakia | Referendum 16/17 May 2003, 92.5% voted "Yes" |
| Slovenia | Referendum 23 March 2003, 89% voted "Yes" |