BACKGROUND: The complexity of the relationship between environmental factors on the one hand and dietary behavior and physical activity on the other necessitates the search for moderators of environmental influences. The current evidence base is reviewed regarding potential moderating factors in the effectiveness of environmental interventions aimed at diet and/or physical activity of children and adolescents. METHODS: The following databases were used: (1) Medline, (2) PubMed, (3) PsychInfo, (4) Web of Science, and (5) ERIC. Additionally, all potentially relevant references in recent reviews were checked. RESULTS: Of the 41 studies included in the review, only seven studies (17%) were identified that reported tests of potential moderators of intervention effects. Gender proved to be the most frequently studied potential moderator. Additionally, race, age, and site have been studied regarding their potential role in modifying the effect of environmental interventions. DISCUSSION: The small number of studies identified in this review prohibited us from attempting to formulate a conclusion on differential environment-behavior relationships in distinct subgroups. Rather than being an exception, it is argued that tests of effect modifiers should become common practice in behavioral nutrition and physical activity research to increase our understanding of mechanisms of behavior change and to optimize interventions.