Although the Proto-Slavic word for lungs can be reliably reconstructed as *pluťa (n. pl.) or *pľuťa (n. pl.), it remains unclear how these two forms are related to each other. Scholars have expressed contradictory views as to which of the two forms should be considered primary. In a number of Slavic languages, the descendants of *pľuťa are more widespread, as they can be found in Old Church Slavonic, Serbo-Croatian, Slovenian, Czech, Slovak, Polish, Lusatian, and Old Russian, whereas the continuants of *pluťa prevail (without being exclusive) in two unconnected areas: Polish-Sorbian-Polabian and Serbo-Croatian-Slovenian. It seems most likely that the form *pľuťa is older and *pluťa is an innovation. The following attempts have been made to explain the relation between the two forms: a) assimilation *pluťa > *pľuťa; b) dissimilation *pljutja > *plutja or *pľuťa > *pluťa; c) *pľuťa > *pluťa under the influence of the infinitive *pluti ‘to fl oat’; d) *pľuťa > *pluťa as a result of the ‘secondary hardening of ľ; e) doubleting *pľuťa / *pluťa because of the twofold development of Proto-Slavic *eu̯ > *u/*ju; f) doubleting *pľuťa / *pluťa as a reflection of two ablaut grades within one athematic paradigm; g) doubleting as a result of vowel assimilation *pleu̯ti̯ā > *plau̯ti̯ā. In our view, the distant dissimilation of the palatals ľ–ť > l–ť or the influence of the underlying verb *pluti ‘float’ should be considered the most probable scenarios of how the variant *pluťa appeared. In terms of word formation, it is likely that feminine *pleu̯tis > *pľutь was the initial form. Having shifted from *-i-declination to *-jā, it came to be perceived as the plural of the neutral noun.