Media companies increasingly place (parts of) their online news content behind to compensate for shrinking digital advertising revenues. However, despite its prominence in the contemporary news environment, very few studies have assessed the effects of this practice on the diversity in the actual content provided to people. To fill this knowledge gap in scholarship, this study examines how diverse free and paid content is in several newspapers in Flanders (Belgium). Using a topic classification model and quantitative analysis of 287,856 online news articles, we differentiate between paywalled and non-paywalled articles, popular and quality news brands, two distinct media corporations and two diversity benchmarks: open and reflective diversity. Our findings reveal that in most cases, online news content behind paywalls is indeed more diverse, although the differences with freely available articles are often minimal. We also find that quality news titles do not necessarily score higher on topic diversity than their popular counterparts. These findings are contextualised within the Flemish media market as well as existing scholarship.