Attempted suicide may be a different phenomenon in adolescents than in adults. To our knowledge, direct comparisons between these two populations are very scarce. The aim of this study is to analyze the differences between adolescents and adults in methods of attempted suicide, accompanying certainty of death, and intentionality. All cases admitted to one adult (n=173) and one adolescent (n=104) inpatient unit who attempted suicide in the period from January 2003 through October 2005 were included in a prospective, common, national register, with data on methods, circumstances, and intentionality. The methodology followed that of the WHO/Euro Multicenter Study on Parasuicide. A stratified analysis was performed using the Mantel-Haenszel procedure in order to control for the effects of gender and diagnosis. Adolescents used significantly more over-the-counter medicines. Adults were significantly more certain of the possible fatal outcome of their attempt and had a significantly more severe intention when harming themselves. Individuals appear to use the methods that are available to them to attempt suicide. Adolescents may display more impulsive and less lethal directed behavior than adults or, alternatively, they are more frequently admitted for less severe attempts.