AIM: To document the prevalence of low back pain (LBP) in Flemish adolescents and to recognize the association between perceived social support and affect and medical consultation and reduction of activities. METHODS: The study comprised 620 adolescents. A questionnaire was used to elicit the characteristics of LBP. Perceived social support and affect were investigated using the Personal Resource Questionnaire (PRQ) and the Positive Affect Negative Affect Scale (PANAS), respectively. Comparisons were made between adolescents with LBP and adolescents without LBP. Within the LBP group, answers from adolescents appealing for medical advice were compared with those who did not seek advice. Another comparison was done between adolescents who reduced their activities and those who did not. Descriptive statistics, the median test for two samples, a chi2 test or Fisher's exact probability test and logistic regression analysis were used for data analysis. RESULTS: Month prevalence of LBP was 24.7%. Thirteen adolescents visited a physician or received treatment, pain severity being the sole factor associated with the decision. Fifteen adolescents reduced their sports activities and 11 reduced or stopped other leisure activities. Pain severity and negative affect were the main associated factors. CONCLUSION: The results of the present study encourage further research on the role of pain perception and the influence of psychosocial factors on back pain in adolescents.