The Children's Depression Inventory (CDI) is a 27-item, symptom-oriented scale for youths aged 7-17. In Portugal some psychometric parameters has never been analyzed before.

To analyse the reliability and construct and concurrent validity of the CDI in a Portuguese adolescents sample.

969 adolescents (59.34% girls), aged 15.80 ± 1.51, answered the Portuguese versions of the CDI and of the Rosemberg Self Esteem Scale (SE). To study the temporal stability, 204 (58.74% girls) respondents answered the questionnaires again after approximately 5 weeks.

CDI mean scores were difference between genders [Girls=10.84 ± 6.025 vs. Boys: 8.90 ± 6.477, p < .001]. The Cronbach's alpha (α) was .85 for the total sample, .83 for the Girls, and .87 for the Boys. Pearson correlations between the test and the re-test was r = .81 for the total sample, r = .78 for the Girls sub-sample and r = .83 for the Boys sub-sample. Based on factorial and parallel analysis, a 4-factors structure was selected for the total sample (variance explained, VE = 38.93%), the Girls (VE = 36.92%) and the Boys (VE = 41.98%). The items content were similar in the total sample and by gender, but the order of the factors was different. The four factors were: “Depression and Negative Self Esteem”, “Ineffectiveness and Somatic Symptoms”, “Anhedonia”, “Interpersonal Problems”. The SE and CDI total scores were negative and statistically (p < .001) correlated in the total sample (r = -.67), in Girls (r = -.69) and in Boys (r = -.63).

The Portuguese CDI has good reliability and validity, showing to be an adequate instrument for measuring depressive symptoms in Portuguese adolescents.