BACKGROUND: Elevated blood pressure (BP) during childhood and adolescence is not so rare and increases the risk of hypertension in adulthood. Physical activity (PA) is considered a key component for the prevention and treatment of hypertension in children and adolescents. Thus, the purpose of our study was to assess the level of PA in Greek adolescents and its relation to BP levels. METHODS: The study included 496 students aged 12-17 years who were enrolled on a volunteer basis. All children were subjected to BP measurement on two different occasions during a routine school day. Demographic, socio-economic and lifestyle characteristics were assessed by means of a standard questionnaire. Information on the frequency and duration of PA and on the amount of time spent on sedentary activities was obtained by the short-form self-administered questionnaire International Physical Activity Questionnaire-IPAQ. RESULTS: The study population was divided in three groups according to the score achieved in IPAQ questionnaire: low PA (n = 39), moderate PA (n = 230) and high PA (n = 231). Children with high PA compared to those with low PA exhibited higher systolic BP and pulse pressure levels, greater prevalence of prehypertension/hypertension status, while heart rate was significantly lower as the level of PA rose (P < 0.05 for all cases). Intense PA was positively correlated to systolic BP (r = 0.139, P = 0.003) and pulse pressure (r = 0.22, P = 0.0001). CONCLUSION: Intense PA is associated with higher systolic BP, pulse pressure levels and lower heart rate in healthy young adolescents. PA should be practiced at a moderate intensity level in everyday life.