This study employs Q-methodology to investigate the criteria adolescents use when evaluating their musical compositions. Thirty-two adolescents (aged 13-14 years) balanced for gender and prior experience of formal instrumental music tuition (FIMT) participated in a Q-sort procedure based on forty-six items. The items were formulated from four sources: specialist music teacher interviews, adolescent focus group discussions, music curriculum documents, and academic papers investigating the assessment of music composition. The resulting data was analysed using factor analysis. In Q-methodology, these factors represent groups of adolescents based on the criteria they considered important for evaluating their musical compositions. Three main groups of adolescents were associated with the majority of participants. The criteria found to be important to each group were interpreted as: (1) composing an appealing piece to a preconceived formula, (2) composing a novel, abstract and interesting piece, and (3) composing an inventive and imaginative piece to a preconceived formula. Comparisons between the criteria used by adolescents and the criteria regarded as important by music teachers are also examined, as well as differences between the adolescents‟ criteria based on their prior experience of FIMT. Suggestions for future research and the implications of the findings for music education are discussed.