Estonian is a morphologically rich Finno-Ugric language with nominal paradigms that have at least 28 different inflected forms but sometimes more than 40. For languages with rich inflection, it has been argued that whole-word frequency, as a diagnostic of whole-word representations, should not be predictive for lexical processing. We report a lexical decision experiment, showing that response latencies decrease both with frequency of the inflected form and its inflectional paradigm size. Inflectional paradigm size was also predictive of semantic categorization, indicating it is a semantic effect, similar to the morphological family size effect. These findings fit well with the evidence for frequency effects of word n-grams in languages with little inflectional morphology, such as English. Apparently, the amount of information on word use in the mental lexicon is substantially larger than was previously thought.