Background <p>Short efficient questionnaires to detect depressive symptoms in adolescents are sparsely evaluated. We aimed to examine the test–retest reliability and structural and convergent validity of the Danish version of the 6-item version of the Hopkins Symptom Checklist-core depression (SCL-6) in adolescents.</p> Methods <p>Our study population consisted of 122 adolescents. Ninety-one adolescents completed SCL-6 (test sample) in the first round, 82 adolescents completed SCL-6 in the second round (retest sample), with 66 completing the questionnaire both rounds (test–retest sample). Reliability was evaluated by intraclass correlation (ICC) and standard error of measurement (SEM), and structural validity was evaluated by confirmatory factor analysis (CFA) and Mokken analyses. Convergent validity was assessed using the 4-item version of the Centre for Epidemiological Studies Depression Scale (CES-DC4).</p> Results <p>The mean sum score in the test sample was higher than in the retest sample (0.74 (95% CI:0.06;1.43)). The limits of agreement (LoA) were broad (-4.73;6.21). The intraclass correlation (ICC(1,1)) was 0.79 (95% CI:0.67;0.87)) showed good reliability, while the SEM (2.03 (95% CI: 1.68; 2.37)) was large considering the range of the scale. Cronbach's alpha showed good internal consistency at both test (0.80) and retest (0.81). The inter-item correlations and Mokken analyses supported the conclusion of a unidimensional scale. The CFA did not find an acceptable fit of a one factor solution. The convergent validity showed a moderate correlation with the CES-DC4 (0.48).</p> Conclusion <p>SCL-6 showed acceptable internal consistency and test–retest reliability. The results from the CFA were inconclusive in terms of demonstrating unidimensionality, but Mokken analyses supported unidimensionality like previous studies. We find the scale usable for population-based research on depressive symptoms in adolescents, but do not recommend it as screening tool on individual level.</p>