Background. The sand lizard Lacerta agilis (Linnaeus, 1758) is widespread throughout Eurasia. So far, several of its subspecies have been described, but only ten of them have been officially recognized. There are two subspecies in Poland: L. agilis agilis and L. agilis argus, but their exact range has not been determined yet. One of the main features that is officially considered an acceptable taxonomic index is the triangular arrangement (1/2) of two postnasal scales (scuta postnasalia) and one loreal scale (scuta frenale). However, in many L. agilis populations, significant deviations from the typical pattern of these scales were found. Methods. 607 sand lizards were caught. 170 in Żary, 150 in Zielona Góra, and 287 in Nowa Sól. The lizards were caught by hand. Their age, sex (adult female, adult male, or juvenile specimens) and the number of sc. postnasalia and sc. frenale were determined. Detailed photographic documentation of each individual was also made. Results. A typical arrangement of postnasal scales and a loreal scale was observed in 83 % of the lizards from Żary, 78.6 % lizards from Zielona Góra and 77 % lizards from Nowa Sól. The most common deviations from the pattern 1/2 occurred in the lizards from Nowa Sól. Their biggest variations related to as many as 9 deviations (1/0, 1/1, 1/3, 2/0, 2/1, 2/2, 2/3, 2/7 and 3/2). 25 % of changes in the arrangement of the scales were detected in males, 27 % of changes were observed in females, and 16 % in juveniles. The 2/2 arrangement was the most common. The lizards from Zielona Góra had the smallest variation of deviations as they occurred only in two patterns, namely 1/1, 1/2 with equal frequency. The scale arrangements that have been described occurred in 25 % of males, 27 % of females and 14 % of juveniles. In lizards from Żary, the changes related to four patterns of deviations. Specifically, the 1/1, 2/1, 2/2 and 3/2, and 2/2 pattern was the most common. Various scale arrangements were observed within the same population in 20 % of males, 15 % of females and 17 % of juveniles. No differences in the occurrence of deviations among the populations (χ2 = 10.83, df = 10, P = 0.37) and between females and males (χ2 = 9.97, df = 1, P = 0.99) were observed, however, considerable differences between adults and juveniles (χ2 = 4.60, df = 1, P = 0.032) were noticed. Conclusion.The results confirmed the observations of other scientists who pointed to a considerable variation in the morphology of sc. postnasalia and sc. frenale in the sand lizards. It was stated that the number and the arrangement of the aforementioned scales is not a reliable and consistent feature that can always be applied in order to consistently identify L. agilis in western Poland. Keywords:Lacerta agilis, taxonomy, morphology, differentiation