[en] Background: More than 90% of vitamin D synthesis is dependent on UV exposure. Photosensitive disorders such as lupus erythematosus, protoporphyria and xeroderma require strict sun avoidance, and vitamin D deficiency has been demonstrated in these patients. Melanoma patients are also instructed to avoid sun exposure and may hence be expected to be vitamin D deficient. Materials and method : Winter and summer vitamin D levels were compared in a group of melanoma patients (n=61) and age- and phototype-matched controls (n=53) without photosensitive disorders. Results : Oral supplementary vitamin D intake was reported in 32.7% of the melanoma patients and in 15.1 % in the control group. Despite oral supplementation, only 25% of the melanoma patients and the controls presented with vitamin D levels of 30 ng/mL or higher. In non-supplemented subjects in the melanoma and control groups, respectively, mean winter vitamin D levels were below the recommended threshold at 12,6 ng/mL vs 13.2 ng/mL, respectively, but not statistically different. These values increased significantly in both groups during the summer to 24.6 and 23.8 ng/mL respectively. Conclusion: Unexpected, significant increases in vitamin D levels were seen in melanoma patients during summer, suggesting non-adherence with photoprotective measures and reflecting a heliophilic behaviour. Vitamin D supplementation is recommended in melanoma patients during both winter and summer.