The notion of ‘productivity’ is an essential one in the study of linguistic morphology, but its definition is indeed challenging, and there are different ways to measure different aspects of the productivity of a morphological process. In this paper we shall adopt Baayen’s P measure of productivity for a corpus-based study of the productivity of three Mandarin derivational suffixes, namely the nominalizer/diminutive −兒 −r, −化 −huà ‘−ise, −ify’ and −頭 −tou, a ‘dummy’nominal suffix (Lin 2001:82), in order to assess how this index relates to our received knowledge about the productivity of such forms, and, also, to compare our results with a previous study by Nishimoto (2003) on a small corpus of Modern Chinese. Moreover, in a diachronic perspective, we shall compare data from the Academia Sinica Tagged Corpus of Early Mandarin Chinese and from the Academia Sinica Balanced Corpus of Modern Chinese. We shall show that our P values mostly reflect what descriptive works tell us about the productivity of the affixes considered here in two different periods of the history of the language; when corpus data for previous stages of a language are available, they appear as a better basis for assessments on the profitability of a morphological process than dictionary data.