BACKGROUND: Epidemiological studies indicate that the prevalence of psychological problems in patients attending primary care services may be as high as 25%. AIM: To identify factors that influence the detection of psychological difficulties in adolescent patients receiving primary care in the UK. DESIGN OF STUDY: A prospective study of 13-16 year olds consecutively attending general practices. SETTING: General practices, Norfolk, UK. METHOD: Information was obtained from adolescents and parents using the validated Strengths and Difficulties Questionnaire (SDQ) and from GPs using the consultation assessment form. RESULTS: Ninety-eight adolescents were recruited by 13 GPs in Norfolk (mean age = 14.4 years, SD = 1.08; 38 males, 60 females). The study identified psychological difficulties in almost one-third of adolescents (31/98, 31.6%). Three factors significant to the detection of psychological disorders in adolescents were identified: adolescents’ perceptions of difficulties according to the self-report SDQ, the severity of their problems as indicated by the self-report SDQ, and whether psychological issues were discussed in the consultation. GPs did not always explore psychological problems with adolescents, even if GPs perceived these to be present. Nineteen of 31 adolescents with psychological difficulties were identified by GPs (sensitivity = 61.2%, specificity = 85.1%). A management plan or follow-up was made for only seven of 19 adolescents identified, suggesting that ongoing psychological difficulties in many patients are not being addressed. CONCLUSIONS: GPs are in a good position to identify psychological issues in adolescents, but GPs and adolescents seem reluctant to explore these openly. Open discussion of psychological issues in GP consultations was found to be the most important factor in determining whether psychological difficulties in adolescents are detected by GPs.