This paper examines the distribution of word lengths in 12 prose texts written in modern Welsh (a P-Celtic language). The texts belong to the genres of new articles and Bible translation. For all texts, the observed frequencies can best be fitted by the 1-displaced Singh-Poisson distribution. This differs from published results on a Q-Celtic language (Scottish Gaelic) and suggests a P-celtic/Q-Celtic difference in word-length distribution. Further work is required to investigate other genres of Welsh as well as the other P- and Q-celtic languages.