Placopsis antarctica is an ornithocoprophilous lichen that has been for a long time confused with P. contortuplicata I. M. Lamb. In our study, we focused on morphological characteristics of P. antarctica thalli. We report biometrical data on dominant morphological structures of P. antarctica thallus: cephalodia, marginal lobes, sorediate pits and soralia. Thalli of P. antarctica were collected at the King George Island, Antarctica and analyzed in a laboratory using a digital microscopy approach. Central cephalodium was found rather elliptic then round-shaped. Mean length/width was found 2.424/1.720 mm. Marginal lobes were found wider at the apex (1.415 mm) than basal part (0.495 mm). Side cephalodia were smaller, their mean length/width was found 1.034/0.610 mm. Key words: cephalodium, morphometry, Nostoc, algae symbiont, microrelief.