Feline eyelid hidrocystoma is a rarely reported disease of the apocrine glands of Moll that has been variably interpreted as proliferative/neoplastic lesion or retention cyst. The purpose of this paper was to investigate feline hidrocystoma pathogenesis by means of a histological and immunohistochemical study. Nine paraffin embedded biopsies of eyelid hidrocystoma were retrieved from our archives. Histological sections were immunostained with antibodies anti-cytoskeletal proteins and Ki67 antigen. All hidrocystomas were observed in Persian cats, seven males/two females, mean age 9.6 years. Histologically, single or multiple, variably sized cysts expanded eyelid dermis. Cyst was lined by cuboidal epithelium, occasionally raising in papillary structures. Immunostaining was consistent with apocrine gland epithelium (cytokeratin 8/18; 19 and 14 positive). Ki67 immunolabelled nuclei ranged from 5.3 to 20.83%. Although it was not possible to draw a definite conclusion concerning hidrocystoma aetiopathogenesis, the relatively high Ki67-proliferative index observed, suggested a proliferative nature of the lesion.