PURPOSE: To assess the contact angle, volume loss and nanoleakeage profile of five one-component self-etching adhesive formulations that differed in their HEMA content, on enamel and dentin. METHODS: Contact angles of drops from each adhesive system were measured over 40 enamel and dentin flat surfaces. Volumetric changes were measured as well. The adhesives were then applied over repolished surfaces according to manufacturers' recommendations, covered with a microfilled restorative composite and the samples were silver infiltrated and prepared for evaluation in a scanning electron microscope. RESULTS: On enamel and dentin surfaces, the contact angles decreased with increasing HEMA content. A correlation was observed between contact angle, volume loss and HEMA content on both substrates.