knowledge of noncommunicable diseases and practices related to healthy lifestyles among adolescents in state schools of a selected educational division in sri lanka background behaviors established during the adolescence have lifelong consequences to the onset of noncommunicable diseases ncds in later life therefore it is essential to understand adolescents knowledge and practices with the intention of developing preventive programs focusing on this age group the objective of the study was to assess knowledge about selected ncds and lifestyle choices among school students aged 1719 years in state schools of the maharagama educational division sri lankamethods a descriptive crosssectional study was conducted among students aged 1719 years attending state schools in maharagama education division a total of 634 students were selected from 9 schools conducting advance level classes stratified sampling was done based on stream of study and the number needed from each stratum was decided according to probability proportionate to size which was followed by cluster sampling within the strata to select the classes included data were collected using a selfadministeredquestionnaire on sociodemographic characteristics and economic status lifestylerelated practices knowledge on noncommunicable diseases logistic regression was used to assess the associationsresults proportion students with good overall knowledge was 43n 272 fortythree percent n 275 consumed a healthy diet and 20n 129 engaged in adequate physical activity 3n 18 of students were current smokers and 12n 73 current alcohol users 12n 73 overall good knowledge about ncds was associated with being a science stream studentor 33 95ci2152 healthy diet was associated with female sex or 21 95ci 1530 and adequate physical activity with male sex or 21 95 ci1432 nonsciencestream or 21 95ci1237 and upper socio economic status or 20 95ci1330 nonsmoking was associated with overall good knowledge or 41 95ci12137 and female sex or 095ci15infinity abstinence from alcohol was associated with being a female or 69 95ci34139 and with mother and fathers education level of generalcertificate of examinations ordinary level gce ol or 29 95ci1184 and or 35 95ci11112 respectivelyconclusion knowledge about ncds and healthy lifestylepractices were poor among school students aged 1719 years lack of knowledge about healthy and unhealthy behaviors highlights the importance of carrying out regular surveillance for ncd risk factors and initiating programs for the prevention of ncds amongst adolescents