The aim of this paper is to compare two Polish predicative constructions with infinitival subjects, namely those with predicative adverbs and those with predicative adjectives. The latter construction, of the form “predicative adjective + copula + infinitival subject”, has hardly been noticed in Polish literature on predication, copulas, or infinitival subjects. On the basis of corpus data, mainly from the National Corpus of Polish, we demonstrate that this construction is much rarer than the analogous construction with predicative adverbs. We also show that roughly the same predicates may be expressed as either adverbs or as adjectives when the subject is an infinitival phrase – any observed differences are not systematic but rather stem from lexical gaps and differences in the meanings of particular adverbs and adjectives. In particular, certain modal predicates may only be expressed as adjectives because the corresponding adverbs do not express the same non-epistemic modal meanings. Finally, we provide new corpus evidence for an earlier claim that predicative adjectives are much rarer than adverbs when the subject is infinitival because they require this subject to undergo covert nominalisation; as adverbs combine with infinitival subjects directly, they are usually preferred.