An EU twinning project entitled 'Strengthening of administrative structures for radiation protection and safe use of ionising radiation in diagnostics and therapy' was established between Bulgaria and Finland, lasting from June 2008 to May 2009. One component of the project was to improve the optimisation of patient protection in nuclear medicine (NM) through revising diagnostic reference levels (DRLs). The revised DRLs are based on national surveys on the numbers of NM procedures and activities given to the patients in different procedures. The survey in Bulgaria was carried out in 2008 and that in Finland in 2007. National DRLs were established for the most frequent and dose-relevant examinations. The proposed DRLs in both countries are in good agreement with other national recommendations in Europe.