Objective: To compare risk of suicide ideation and attempts in adolescents with 1) gay, lesbian, or bisexual (GLB) identity, 2) "unsure" identity, or 3) heterosexual identity with same-sex attraction/fantasy or behavior, to heterosexual identity without same-sex attraction/fantasy or behavior. Method: A total of 1,856 students 14 years of age and older from 14 public and private high schools in Montreal, Quebec, were surveyed anonymously. The survey included items assessing sexual orientation, health risk behaviors, and suicidal ideation and attempts. Multiple logistic regression models were used to assess risk factors for suicidal ideation and attempts. Results: In all, 58 (3.1%) adolescents self-identified as GLB, 59 (3.2%) as unsure, and 115 (6.2%) as heterosexual with same-sex attraction/fantasy or behavior. Compared with heterosexually identified youth without same-sex attraction/fantasy or behavior (N = 1,624; 87.5%), in multivariable analyses, 12-month suicidal ideation was significantly higher for both GLB (odds ratio [OR] = 2.31, 95% confidence interval [CI] = 1.22-4.37) and unsure youth (OR = 2.64, 95% CI = 1.38-5.08). Twelve-month suicide attempts were significantly elevated for GLB youth (OR = 2.23, 95% CI = 1.15-4.35) and high, although not statistically significant, for unsure youth (OR = 1.61, 95% CI = 0.77-3.36). Heterosexual identity with same-sex attraction/fantasy or behavior was not significantly associated with increased suicidal ideation (OR = 1.26, 95% CI = 0.76-2.08) or attempts (OR = 1.03, 95% CI = 0.55-1.91) in multivariable analyses. Conclusion: Compared with heterosexual youth without same-sex attraction/fantasy or behavior, adolescents with GLB and unsure identities were at greater risk of suicidality. However, youth who reported same-sex attraction or behavior but a heterosexual identity were not at elevated risk. (Contains 3 tables.)