This paper tests whether lemma frequency impacts the duration of homographic noun–verb homophones in spontaneous speech, e.g. cut (n)/cut (v). In earlier research on effects of lemma frequency (e.g. Gahl 2008), these pairs of words were not investigated due to a focus on heterographic homophones. Theories of the mental lexicon in both linguistics and psycholinguistics differ as to whether these word pairs are assumed to have shared or separate lexical representations. An empirical analysis based on spontaneous speech from the Buckeye corpus (Pitt et al. 2007) yields the result that differences in lemma frequency affect the duration of the N/V pairs under investigation. First, this finding provides evidence for N/V pairs having separate representations and thus supports models of the mental lexicon in which lexical entries are specified for word class. Second, the result is at odds with an account of ‘full inheritance’ of frequency across homophones and consequently with speech production models implementing inheritance effects via a shared form representation for homophonous words. The findings are best accounted for in a model that assumes completely separate lexical representations for homophonous words.