The article is focused on Russian constructions with zero copulas. I test constructions with zero copulas for compatibility with different syntactic contexts to find out whether their syntactic behavior differs significantly from that of lexical verbs. The diagnostics used in the paper include occurrence in relative and temporal clauses, compatibility with particles, and adverbials / adverbial constructions. The differences between the zero copulas and lexical verbs turn out to be of two types: a copula allows some uses, prohibited for lexical verbs, and, in contrast, is impossible in other constructions where lexical verbs can participate. The differences are due to two properties of copulas: (1) lack of morphologically-marked categories and (2) lack of a lexical stem. Different types of copulas as distinguished by Testelets (2008) behave differently in syntactic tests, but the picture cannot be reduced to Testelets' two classes of copulas (binominative and non-binominative ones).