Research indicates the need to further examine the dimensions of reading motivation. A clear theoretical basis is necessary for conceptualizing reading motivation and considering contextual differences therein. The present study develops and validates the SRQ-Reading Motivation, a questionnaire measuring recreational and academic reading motivation based on self-determination theory. The study clarifies the relation among reading motivation, reading self-concept, reading behavior (i.e., engagement and frequency), and reading performance (i.e., comprehension). Participants included 1,260 Flemish fifth-grade students and their 67 teachers. Exploratory and confirmatory factor analyses indicated that both recreational and academic reading motivation comprise 2 factors: autonomous and controlled motivation. This factor structure was found to be invariant across boys and girls. Comparisons of the SRQ-Reading Motivation with subscales of the Motivation for Reading Questionnaire provide evidence for the construct validity of the instrument. Structural equation modeling confirmed that recreational autonomous reading motivation is associated with more positive reading behavior and better performance. In the academic setting, only the equivalent relationship between autonomous reading motivation and leisure-time reading frequency could be corroborated. In this respect, the results confirm the independent contribution of recreational autonomous reading motivation and reading self-concept to reading behavior and performance. No significant indirect relationship between reading motivation and reading comprehension through reading frequency or reading engagement was found. The theoretical and practical significance of the present study is discussed. (Contains 5 tables, 4 figures and 3 footnotes.)