Background: The prevalence of depression and anxiety in patients after acute coronary syndrome (ACS) is higher than in the general population. In a study on prevention of post-ACS depression, more than half of eligible patients declined participation. Aims: The aim of this study was to evaluate whether symptoms of depression and anxiety in participants and non-participants predicted participation in the study. Methods: This substudy was conducted between May 2005 and April 2007. Patients with ACS, eligible for the study (n=302) were asked four questions on depression and anxiety from the Primary Care Evaluation of Mental Disorders (PRIME-MD) screening questionnaire. Results: The PRIME-MD screening data were available on 232 patients (76.8% of eligible patients). Thirty-eight (35.5%) of 107 participants and 30 (24.0%) of 125 non-participants had a positive screening for depression (NS), and 47 (43.9%) participants and 55 (44%) non-participants were screened positive for anxiety (NS). Non-participants were older (P=0.002), while no significant differences in gender or cardiac diagnosis were found. Conclusions: Symptoms of depression and anxiety were highly prevalent in patients after ACS but did not predict participation in the study of prevention of depression.