The paper is aimed at studying the texts of Russian Constitutional Court decisions, issued from 1992 to 2018. We analyzed the corpus, consisting of 584 decisions or 3,426,747 tokens (incl. punctuation marks) and tested the hypothesis about increasing lexical complexity of the documents. Using the R package stylo and MFW statistics, we got a picture that reflects the differences of the texts by years. The results of cluster analysis show that the texts of the 90s and 2000s are combined into the first large cluster. The second large cluster includes the texts of the 2010s. Using the R package quanteda, we obtained the values of 11 lexical diversity measures. We chose the index K (Yule’s K) as a basic measure, relatively more reliable and independent of the text length, and then interpreted the values of this measure. In general, the value of K decreases over the years, except for the texts of 2006, in which there is a noticeable increase in the index value, and the texts of 1993, in which the outlier is observed. The calculation hapax proportion shows a picture of a gradual decrease in the share of hapaxes. If we apply the traditional approach to the interpretation of TTR values and derived metrics, we can conclude that, as the lexical diversity decreases and the proportion of hapaxes decreases, the texts become easier to read.