The research shows that one of the key determinants of consumer satisfaction is disconfirmation, which refers to the perceived differences between product performance and pre-purchase expectations. In this case, positive disconfirmation (when performance exceeds expectations) leads to high, and negative (when it concedes to expectations) to low satisfaction. The present study examined the role of involvement in the occurrence of assimilation effects (a decrease in disconfirmation scores and a shift in satisfaction scores towards expectations) and contrast effects (an increase in disconfirmation scores and a shift in satisfaction scores in the opposite direction), as well as the processes leading to contrast effects. And two hypotheses have been formulated that involvement will produce contrast effects and that such effects will result from the activation of cognitive processes leading to increased perceived differences between product performance and expectations. The hypotheses were tested in a laboratory experiment that manipulated product performance (a screen cleaner quality), expectations and participant involvement levels, and explored two types of assimilation/contrast effects, negative and positive, resulting from high and low expectations for the product. The experiment showed that involvement did produce negative and positive contrast effects in the disconfirmation and satisfaction scores with one exception: involvement did not produce positive contrast effect in the satisfaction scores. The article discusses the possible reasons for this result. The experiment also supported the existence of a chain of processes leading to contrast effects, in which involvement increases the activation levels in subjects, activation stimulates cognitive activity, cognitive activity increases judgment accuracy in product evaluations, and judgment accuracy enhances perceived differences between product performance and expectations. Limitations, questions for future research and implications for manufacturers and retailers from assimilation/contrast effects are discussed.