Suicide has become a leading cause of mortality and morbidity for adolescents in Hong Kong. This study investigated the factors associated with suicidal ideation and attempt among the secondary school students in Hong Kong by studying a representative sample of 3383 students with a self-administered questionnaire and analysed by multiple logistic regressions analysis. Youth risk behaviours, such as heavy smoking, episodic heavy alcohol drinking, early sexual experience, and feeling hopeless, were found to be associated with both suicidal thoughts and attempts, with ‘misuse of drugs’ as discriminating factor that solely related to attempt and ‘involvement in physical fight’ solely related to suicidal thoughts. Addition of suicidal ideation is a significant explanatory variable of suicidal attempt over and above health risk behaviours. Stratified analysis of upper and lower secondary students would give better understanding of significance of various risk factor for different age groups. The disturbing prevalence of suicidal behaviour and its coexistence with other high-risk behaviour in secondary school students have implications for teachers, youth workers and public health practitioners to develop and evaluate programmes for suicide prevention.