The aim of the study was to evaluate the stomach chambers of Zielonogorskie (Z) and Bieszczady (B) red deer (Cervus elaphus L. 1758) from different foraging habitats in South-West and South-East Poland. Thirteen calves, ten hinds and bulls were shot in Z and B, and examination of the carcasses indicated the substantial impact of foraging strategies in various habitats on polygastric parameters. Differences (P<0.05) in stomach content (SC), fresh and dry matter of stomach tissue (FSTM, DSTM) and total stomach area (TSA) were noted between the deer of Z and B. Additionally, some indexes (IA, IB) of FSTM, DSTM in relation to body mass (carcass weight, C) were relatively higher in each category of deer from the B region. Comparisons of ID (ratio DSTM to TSA), IE (DSTM to metabolic body mass - C0.75) and IF (TSA to C0.75 ) indicated a relatively thicker stomach tissue wall, and its larger overall area and volume of some stomach chambers in deer from the B vs. Z region. The study indicates that the carrying capacity of habitats, and conditions such as the quality and abundance of plants (their structure and nutritional value) considerably influence modifications within the digestive system, and mainly the stomach chambers in polygastric wild ruminants.