<p>The study examines whether the order of presentation of affective pictures influences the subjective evaluation of their affective valence and arousal. Seven unpleasant, neutral, and pleasant pictures were presented at the beginning and at the end of the session to check a possible effect of novelty or habituation. The other seven unpleasant, neutral, and pleasant pictures were presented after unpleasant, neutral, and pleasant pictures to check if the affective valence of a previous picture influenced the evaluation of the next one. The results showed some influence of the order of presentation on affective valence - unpleasant pictures at the end were less unpleasant than unpleasant pictures at the beginning, and the neutral picture, when presented after unpleasant pictures, was more pleasant than when presented after pleasant pictures. No effect of the order of presentation on arousal was found. These findings suggest that several orders of picture presentation should be used in future experiments on emotions to avoid possible effects of the order on affective valence.</p>