Perceiving speech is not only dependent on the quality of speech sounds or the listening environment. Numerous studies in the last 10 years have demonstrated that cognitive factors and predictive mechanisms play a significant role on the perceived clarity of speech. In a series of behavioural and neuroimaging studies, I will present which cognitive factors can influence speech perception for both normal-hearing and hearing-impaired listeners, and how predictive mechanisms at phonological and semantic levels can independently and cumulatively enhance speech perception.