Abstract Background The aims of this cross-sectional study were to investigate the regulatory compliance of Dutch practice websites offering orthodontic services, readability of the available treatment information, website design as well as possible relationship with practice location and professional qualification of practitioners. Methods A comprehensive Internet search was performed using the Google search engine and five relevant terms in Dutch. Eligibility screening of the first 50 results of each search led to the final inclusion of 111 websites. The content of the selected websites was evaluated in terms of compliance to international regulations on ethical advertising guidelines (CED), treatment information text readability using Flesch Reading Ease Score (FRES), and website design using the BDC assessment tool. Results Reporting of websites according to CED guidelines covered on average 85% of the mandatory items. No significant differences were observed between dental and orthodontic practices, and between practices located in densely and sparsely populated regions (P > 0.05). The mean FRES of the displayed information indicated difficult-to-understand text. BDC scores of multi-location practices were significantly higher than the rest (P < 0.006). Conclusions The websites of orthodontic practices in The Netherlands do not fully comply with CED guidelines on ethical advertising. Readability of the displayed information and website technical performance needs to be further optimized.