Background The existence of socioeconomic differences in dietary behaviors is well documented. However, studies exploring the mechanisms behind these differences among adolescents using comprehensive and reliable measures of mediators are lacking. The aims of this study were (a) to assess the psychometric properties of new scales assessing the perceived rules and accessibility related to the consumption of vegetables and soft drinks and (b) to explore their mediating role in the association between parental education and the corresponding dietary behaviors. Methods A cross-sectional survey including 440 adolescents from three counties in Norway (mean age 14.3 years (SD = 0.6)) was conducted using a web-based questionnaire. Principal component analysis, test-retest and internal reliability analysis were conducted. The mediating role of perceived accessibility and perceived rules in the association between parental education and the dietary behaviors was explored using linear regression analyses. Results Factor analyses confirmed two separate subscales, named “accessibility” and “rules”, both for vegetables and soft drinks (factor loadings >0.60). The scales had good internal consistency reliability (0.70–0.87). The test–retest reliability of the scales was moderate to good (0.44–0.62). Parental education was inversely related to the consumption of soft drinks and positively related to the consumption of vegetables. Perceived accessibility and perceived rules related to soft drink consumption were found to mediate the association between parental education and soft drink consumption (47.5 and 8.5 % of total effect mediated). Accessibility of vegetables was found to mediate the association between parental education and the consumption of vegetables (51 % of total effect mediated). Conclusion The new scales developed in this study are comprehensive and have adequate validity and reliability; they are therefore considered appropriate for use among 13–15 year-olds. Parents, in particular those with a low educational background, should be encouraged to increase the accessibility of vegetables and to decrease the accessibility of soft drinks, in particular during dinner. Enforcing parental rules limiting soft drink intake in families with low parental education also appears relevant.