Children learn high phonological neighbourhood density words more easily than low phonological neighbourhood density words (Storkel, 2004). However, the strength of this effect relative to alternative predictors of word acquisition is unclear. We addressed this issue using communicative inventory data from 300 British English-speaking children aged 12 to 25 months. Using Bayesian regression, we modelled word understanding and production as a function of: (i) phonological neighbourhood density, (ii) frequency, (iii) length, (iv) babiness, (v) concreteness, (vi) valence, (vii) arousal, and (viii) dominance. Phonological neighbourhood density predicted word production but not word comprehension, and this effect was stronger in younger children.