Standardized instruments are crucial for a valid assessment of suicidal behavior. In questionnaire assessments the wording of questions can influence the results. In this study we compared the congruence of the Self-Harm Behavior Questionnaire (SHBQ) and the Ottawa Self-Injury Inventory (OSI) as measures of prevalence of suicidal ideation in an adolescent sample (n = 665, mean age: 14.8, SD: 0.66). We found a life-time prevalence of 36.4 % in the SHBQ and a one-year-prevalence of 27.8 % in the OSI. There was good agreement between the two instruments in terms of the prevalence of suicidal ideation and the association with suicide attempts. The observed rates are comparable with other studies in adolescents; differences arise with varying study designs.