The purpose of this study is to determine healthy life style behaviours, such as average daily sleep duration, sport habit, physical activity level and eating habits, of high school students in their middle adolescence (15-17 ages). The research sample consists of 642 (n=338 male and n=304 female) volunteer students in a secondary education institution in Konya city centre. The questionnaire formed by examining relevant literature has been used to determine healthy life style behaviours. The average daily sleep duration of the students participating in the study is 8.30±1.26. 42.8% the of female students and 37.8% of the male students do not do sports. 69.8% of the female students and 74.6% of the male students use the internet from their mobile phones during the day. The percentage of those who watch television 1-3 hours and more a day is 85.6% for the female students and 81.6% for the male students. 28.2% of the female students and 30.2% of the male students skip meals. 38.8% of the female students and 36.1% of the male students have breakfast. Within the lights of the findings in the survey, it has been concluded that the students in middle adolescence do not healthy life style behaviours sufficiently. The students do not consume the eatables that are healthy for them. The food stuffs, such as chips, chocolate, carbonated drinks and hamburgers, whose overconsumption is harmful to are frequently consumed by students. It should not be forgotten that the eating habits obtained in the adolescence will affect the adulthood period. Therefore, evaluating their nutritional status, adolescents should be gained adequate and balanced nutrition habits. In the adoption of a healthy lifestyle, adequate balanced nutrition and physical activity should be considered as a whole and, when required, a specialist health professional should be consulted for proper nutritional advice.