Only a few studies have been published concerning dissociation in general population adolescents. We assessed dissociation using the Adolescent Dissociative Experiences Scale (A-DES) in a sample of Finnish adolescents aged 13 to 18 years (n = 4019). The A-DES had good internal reliability and factor analysis suggested a 1-factor solution to be optimal. The younger participants had somewhat higher A-DES scores, but there were no differences between the genders. The mean A-DES score of 0.88 in the whole sample was lower than that in previous studies in other countries. A high level of dissociation was associated with an age of 15 or less, daily smoking, frequent use of alcohol, abuse of legal drugs, cannabis use, social isolation, and poor school performance in mathematics.