Objective: The first nationwide Israel Survey of Mental Health Among Adolescents was conducted in 2004-2005 with a representative sample of 957 adolescents aged 14-17 and their mothers to assess 12-month mental health service use, unmet needs, and associated factors. Methods: Need for services was assessed by presence of a psychiatric disorder diagnosed with the Development and Well-Being Assessment inventory, plus clinicians' verification and additional questions on service use. Results: In the past year, 22% of adolescents and 11% of their mothers consulted a service provider. Adolescents' help seeking in school was associated with residing in an Arab locality (odds ratio [OR]=1.6, 95% confidence interval [CI]=1.1-2.4) and with having single, divorced, or widowed parents (OR=2.9, CI=1.8-4.8); an employed father (OR=1.7, CI=1.0-2.8); and an internalizing disorder (OR=2.2, CI=1.2-3.9). Mothers' consultation was associated with residing in a Jewish or mixed locality (OR=18.1, CI=3.4-96.1); being single, divorced, or widowed (OR=3.1, CI=1.6-6.0); and having a child with an internalizing disorder (OR=6.4, CI=3.2-13.0), an externalizing disorder (OR=8.2, CI=2.9-23.0), or a learning disability (OR=4.5, CI=2.4-8.4). Overall, unmet needs were 66% and 60%, according to adolescents' and mothers' reports, respectively. According to mothers' reports, unmet needs were higher in Arab (91%) than in Jewish or mixed localities (54%). Conclusions: Adolescents and their mothers reported distinct service use patterns with particular implications for policy makers and health service providers. High rates of unmet needs, particularly among Arab-Israeli adolescents, need to be addressed.