Background Several studies with conflicting findings have investigated the association between acne and mental health problems. Acne usually starts in adolescents, as does an increase in the prevalence of depression and anxiety. Recently, there has been more focus on the link between diet and acne and diet and mental health problems. The objective of this study is to investigate the association between acne and mental distress and to explore a possible influence of dietary factors on the relation. Methods A population-based cross-sectional study in Oslo of 18 or 19 year old adolescents. The participation rate was 80%. Acne was self-reported. To measure mental distress, the Hopkins Symptom Checklist 10 was used. Diet and lifestyle variables were also collected by questionnaire and socio-demographic variables were obtained from Statistics Norway. Results The prevalence of acne was 14.4% among the males and 12.8% among the females. The mean score of mental distress increased when the severity of acne increased. In the crude analyses, the significant associations with acne among the males were: mental distress OR = 1.63, frequent consumption of chocolate/sweets OR = 1.40, frequent consumption of potato chips OR = 1.54. The significant crude associations with acne among the females were: mental distress OR = 2.16, infrequent consumption of raw vegetables OR = 1.41, non-Western background OR = 1.77 and low family income OR = 2.14. No crude associations with acne were identified in either gender for the consumption of sugary soft drinks, fatty fish, cigarette smoking or alcohol. In adjusted models which included diet and socio-demographic variables, the association between acne and mental distress was unchanged for both males (OR = 1.68) and females (OR = 2.04), and between acne and infrequent consumption of raw vegetables among the females (OR = 1.38). Conclusion Among late adolescents in Oslo, self-reported acne is significantly associated with mental distress and, among girls, with infrequent consumption of raw vegetables. Our finding does not support the hypothesis that dietary factors alter the relationship between acne and mental distress.