Hearing-impaired people often complain that they have a hard time understanding speech in noisy environments and in rooms with high reverberation levels. There are several effects of reverberation which can reduce speech intelligibility in noise. Most of them have been studied with normal-hearing listeners. In the case of hearing-impaired listener these effects are often mixed, and it is hard to determine in which noise environments and rooms hearing impaired listeners have more difficulties to understand speech. The goal of this study was to determine the importance of two monaural effects of reverberation for normal hearing and hearing-impaired listeners. The first one is the temporal smearing of the target speech, which decreases its intelligibility. The second one is the temporal smearing of a modulated noise, which makes it more difficult to listen in the masker dips. To separately evaluate these two effects, reverberation was applied either on the target speech, on the noise masker or on both sources. Bayesian analyses were done to compare the intelligibility scores of the normal hearing and hearing-impaired listeners in these situations.