Background The use of screening instruments can reduce waiting lists and increase treatment capacity. The aim of this study was to examine the usefulness of the Strengths and Difficulties Questionnaire (SDQ) with the original UK scoring algorithms, when used as a screening instrument to detect mental health disorders among patients in the Norwegian Child and Adolescent Mental Health Services (CAMHS) North Study. Methods A total of 286 outpatients, aged 5 to 18 years, from the CAMHS North Study were assigned diagnoses based on a Development and Well-Being Assessment (DAWBA). The main diagnostic groups (emotional, hyperactivity, conduct and other disorders) were then compared to the SDQ scoring algorithms using two dichotomisation levels: 'possible' and 'probable' levels. Sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio (ORD) were calculated. Results Sensitivity for the diagnostic categories included was 0.47-0.85 ('probable' dichotomisation level) and 0.81-1.00 ('possible' dichotomisation level). Specificity was 0.52-0.87 ('probable' level) and 0.24-0.58 ('possible' level). The discriminative ability, as measured by ORD, was in the interval for potentially useful tests for hyperactivity disorders and conduct disorders when dichotomised on the 'possible' level. Conclusions The usefulness of the SDQ UK-based scoring algorithms in detecting mental health disorders among patients in the CAMHS North Study is only partly supported in the present study. They seem best suited to identify children and adolescents who do not require further psychiatric evaluation, although this as well is problematic from a clinical point of view.