Adolescents are becoming less physically active and are increasingly adopting a sedentary life-style in front of computers and television screens. In this chapter we look at self-related health, physical activity, sleeping habits, the prevalence of overweight and body complaints in two senior high schools with questions about weight and height, health, physical activity, type of physical activity/sport, intensity, sleeping habits and possible injuries or complaints during the last three months. Seventy seven percent % of the high school students participated in sports on a regular basis. In academic programs compared to vocational programs, more males and females in academic programs participated in sports (71% and 80% respectively). Males reported significantly better health than females, but 65% reported body complaints during the last three months. A higher number of females than males reported back and hip complaints. Good sleep was reported in 82.1% of the males (76.6% of the females). In males 44.3% were often sleepy in the daytime (females 56.6%). Underweight, physical activity and good sleep were found to be factors with significant positive effect on good health, whereas overweight was a negative factor. Proper sleep habits and higher physical activity levels should be promoted among high school students and TV viewing time and video game use restricted. Additionally, schools should provide opportunities for young people to participate in a wider range of physical activities that address their individual needs, while promoting the health benefits of engaging in regular exercise.