This study is a comparison of the validity of theory of reasoned action and theory of planned behavior as applied to the area of moral behavior (i.e., illegal copying of software) using structural equation modeling. Data were collected from 181 university students on the various components of the theories and used to asses the influence of attitude, subjective norm, and perceived behavioral control on the intention to make unauthorized software copies. Theory of planned behavior was found to be better than (...) the theory of reasoned action in predicting unethical behavior. A modified version of the theory of planned behavior, with a causal path linking subjective norm to attitude, provided a significant improvement on model fit. The results indicated that perceived behavioral control is a better predictor of behavioral intention then attitude. The direct effect of subjective norm on behavioral intention was not significant, but the indirect effect through attitude was highly significant. Applicability of the theory of planned behavior for moral behavior and the implications for future research are discussed. (shrink)