Using a prospective design and a representative sample of 25-yr-old Norwegians, this study hypothesized that action planning and coping planning will add to the prediction of flossing at 4 wk of follow-up over and above the effect of intention and previous flossing. This study tested the validity of a proposed 3-factor structure of the measurement model of intention, action planning, and coping planning and for its invariance across gender. A survey was conducted in three Norwegian counties, and 1,509 out of 8,000 randomly selected individuals completed questionnaires assessing the constructs of action planning and coping planning related to daily flossing. A random subsample of 500 participants was followed up at 4 wk with a telephone interview to assess flossing. Confirmatory factor analysis (CFA) confirmed the proposed 3-factor model after respecification. Although the chi-square test was statistically significant [χ2 = 58.501, degrees of freedom (d.f.) = 17), complementary fit indices were satisfactory [goodness-of-fit index (GFI) = 0.99, root mean squared error of approximation (RMSEA) = 0.04]. Multigroup CFA provided evidence of complete invariance of the measurement model across gender. After controlling for previous flossing, intention (β = 0.08) and action planning (β = 0.11) emerged as independent predictors of subsequent flossing, accounting for 2.3% of its variance. Factorial validity of intention, action planning and coping planning, and the validity of action planning in predicting flossing prospectively, was confirmed by the present study.