The effect of various dietary supplements on chronic diseases and mortality has been widely studied, but few convincing results have emerged from studies in well-nourished populations. In Norway, both cod liver oil and other dietary supplements are frequently used. In the Norwegian Women and Cancer cohort study, we explored if supplement use before diagnosis affected survival of cancer patients with solid tumours. We performed Cox proportional hazards analyses, adjusting for age at diagnosis, smoking and stage. Cod liver oil was the most frequently used dietary supplement, followed by multivitamins and minerals. Whole year daily use of cod liver oil was associated with lower risk of death in patients with solid tumours [RR = 0.77 (95% CI 0.61-0.97)] and in lung cancer patients [RR=0.56 (95% CI 0.34-0.92)]. Also daily and occasional use of other dietary supplements decreased the risk of death among lung cancer patients [RR = 0.70 (95% CI 0.49-0.99) and 0.55 (95% CI 0.31-0.97)]. More research is needed to clarify the association; meanwhile adjustment for dietary supplement use should be performed in survival analyses of lung cancer patients.