Purpose. The purposes of this study were 1) to examine the differences in suicidal ideation and psychological variables by gender, 2) compare the contribution of demographic-behavioral variables and psychosocial variables in explaining the variance in suicidal ideation, and 3) identify the most important predictors of suicidal ideation for male adolescents and female adolescents. Methods. The subjects consisted of 271 male adolescents and 230 female adolescents. Data were collected through self-report questionnaires, which were constructed to include SSI-C, DEP subscale of the SCL-90-R, PACI, and SWLS. The data were analyzed by the SPSS/WIN program. Results. Suicidal ideation differed by gender. Depression and family communication differed by gender. The unique contribution of demographic-behavioral variables and psychosocial variables in explaining the variance in suicidal ideation differed between male adolescents and female adolescents. The significant predictors of suicidal ideation for male adolescents were life satisfaction, depression, and family communication, explaining $28\%$ of the variance in suicidal ideation. The significant predictors of suicidal ideation for female adolescents were depression, smoking, and life satisfaction, explaining $38\%$ of the variance in suicidal ideation. Conclusion. The findings of this study suggest that the approach to effective suicide prevention program for adolescents should consider gender differences.