Background: It is commonly assumed that there is conceptual equivalence between the task and ego achievement goals proposed by Nicholl's (1989) dichotomous achievement goal theory (Nicholls, 1989), and the mastery and performance approach goals advanced by Elliot's (1997) trichotomous hierarchical model of approach and avoidance achievement motivation. Aims: Our study examined whether this conceptual equivalence is reflected in measurement equivalence by examining the factorial structure and predictive validity of two established questionnaires that assess achievement goals based on Nicholl's and Elliot's approaches to achievement motivation. Sample: Greek adolescents (N = 336, M age = 13.45 years, SD = 1.04). Measures: The participants completed the Task and Ego Orientation in Sport Questionnaire (Duda & Nicholls, 1992), the Approach-Avoidance Achievement Goals Questionnaire (Elliot & Church, 1997) and a Physical Education (PE) version of the Self-Regulation Questionnaire (Goudas, Biddle, & Fox, 1994). Results: Confirmatory factor analyses of a number of competing models showed that a model with five correlated independent factors had the best fit. This finding suggests that the goals measured by the two achievement goal questionnaires are related, although independent constructs. However, hierarchical regression analyses predicting regulatory styles in PE showed quite a substantial overlap between the mastery and performance approach goals proposed by Elliot (1997), and the task and ego goals, respectively, advanced by Nicholls (1989). Conclusions: Taken together, our results indicate that the self-referenced and comparative goals of the TEOSQ and AAGQ are substantially related, to the extent that they have minimal unique predictive validity; however, they are not identical constructs.