He studied with F. Severi and G. Veronese in Padova, where he took is degree in 1908 and soon became assistant of Severi. He taught in Cagliari (since 1920) and Padova (since 1922). He was a member of the Accademia Nazionale dei Lincei.

Comessatti is the most prominent Italian scholar in real algebraic geometry.

Among his students we cite U. Morin, A. Predonzan, M. Baldassarri.

Main commemorations: L. Berzolari, Rend. della R. Acc. Nazionale dei Lincei , (8), 1, 1946, 810-815; F. Severi, Boll. dell' Unione Mat. Ital. , (3), 1, 1946, 59-61.