Recent studies found facilitative effects of structural priming on sentence comprehension in sentences with temporary ambiguities. The present study used the self-paced reading task to test if Czech sentences with and without ambiguities could be affected by structural priming. The target sentences were similar to the English and German structures that were shown previously to undergo structural priming of predictive processing. Experiment 1 found structural facilitation in the temporarily ambiguous sentences but not in the unambiguous sentences. In Experiment 2, the temporary ambiguity was removed from the ambiguous sentences, and the unambiguous sentences were modified to increase the processing load they posed on the comprehension system. The structural priming effect disappeared in Experiment 2. The results indicate that structural priming of on-line processing is only possible for ambiguous sentences, perhaps because it influences the revision stage of parsing. The implications of the findings for different parsing models are discussed.