A cross-sectional study was conducted among 602 Belgian adolescents to analyse their sun protection habits. The results show that Belgian adolescents stay in the sun for a long time, even in periods when ultraviolet radiation is very damaging. Of all respondents, 70% exposed themselves for at least 3 h to the sun on sunny days. Most respondents (49%) exposed themselves between 1200 and 1500 h. Almost two-thirds of the respondents (59.3%) reported at least one sunburn in the past year and 26.5% got sunburnt at least twice; 24% used sunbeds more than 6 times per year. Applying sunscreen every 2 h was the most commonly used method by adolescents to protect themselves, although 70% did not use sunscreen regularly. Female students used sunscreen more regularly than male students, and sunbed use was higher among 18-year-olds than 14-year-olds. Our results clearly suggest that respondents with fair skin types are at increased risk of developing skin cancer, because of various high exposure activities accompanied by relatively few protection behaviours. A second risk group consists of students from the two lower educational levels, again because of high exposure levels and less frequent protection behaviours. The risks of sunbed use should be communicated clearly to older adolescents. Hence, these two groups need to receive high priority for cancer prevention activities in Belgium.