In the article, we present analyses and findings which add precision to the role of intentions and the relation between effects in attributing the intentionality of causing a side effect. Our research supplements and modifies numerous findings regarding the appearance of the so-called Knobe effect. The experiments and analyses show that the very originality of the story used by Knobe and the relationship between the evaluative properties of the main effect and the side effect results in an asymmetry of responses and contributes to the occurrence of the side-effect effect. Because of this, we reject the thesis that the mode of attitude of the agent to the caused side effect or that the social expectation of this attitude determine the attribution of the intentionality of the caused effect. On the contrary, we defend the thesis that it is the relationship between the evaluative properties of the main effect and those of the side effect, as well as the impact of a side effect on the main effect, that significantly influence the attribution of intentionality in causing a side effect.