This study investigated the extend to which the snail <em>Columella edentula</em> is more strongly associated with the small balsam <em>Impatiens parviflora</em> than with other plants in the herb layer of an oak-hornbeam forest, and to interpret the character of the interaction <em>Impatiens parviflora</em> - <em>Columella edentula</em>. Numbers of <em>C. edentula</em> and rates of colonization were compared on various plant species under natural and laboratory conditions. Seasonal variation in snail abundance on <em>I. parviflora</em> was observed on permanent plots. The leaf injuries caused by <em>C. edentula</em> were localized in respect of the morphological and anatomical structure of leaves. The results show that <em>I. parviflora</em> is one of the plant species of the herb layer that are most abundantly colonized by this snail in oak-hornbeam forest. Snail finds a plant particularly suitable as a place for resting. The most favoured attachment site is on the underside of the leaf, along the midrib, which provides the highest and relatively stable humidity, as well as protection from direct sunlight and predators. <em>I. parviflora</em> is also a food for the snails, but they do not eat these fragments of leaves where calcium carbonate is accumulated.