In this article I reanalyze sibilant inventories of Slavic languages by taking into consideration acoustic, perceptive and phonological evidence. The main goal of this study is to show that perception is an important factor which determines the shape of sibilant inventories. The improvement of perceptual contrast essentially contributes to creating new sibilant inventories by (i) changing the place of articulation of the existing phonemes (ii) merging sibilants that are perceptually very close or (iii) deleting them. It has also been shown that the symbol š traditionally used in Slavic linguistics corresponds to two sounds in the IPA systemsystem: it stands for a postalveolar sibilant (ʃ) in some Slavic languages, as e.g. Bulgarian, Czech, Slovak, some Serbian and Croatian dialects, whereas in others like Polish, Russian, Lower Sorbian it functions as a retroflex (s). This discrepancy is motivated by the fact that ʃ is not optimal in terms of maintaining sufficient perceptual contrast to other sibilants such as s and ç. If ʃ occurs together with s and sj there is a considerable perceptual distance between them but if it occurs with ç in an inventory, the distance is much smaller. Therefore, the strategy most languages follow is the change from a postalveolar to a retroflex sibilant.