Background: The introduction of resin composite was a revolution in dentistry and it has shown a high level of success as a direct restorative material. Appropriate techniques and light curing units are essential for optimal clinical outcomes. Objective: To assess depth of cure of two bulk-fill composites and one nanofill resin composite, when photopolymerized with two different curing light units (CLU), placed with an incremental layering versus bulk-fill technique. Material and methods: Two Bulk-fill resin composites (Surefil SDR® Flow and Tetric EvoCeram®) and a conventional nanofill (FiltekTM Supreme Ultra) were used to prepare 90 cylindrical specimens. Specimens (n=5/group) were made using two placement techniques (incremental and bulk-fill). Each specimen was polymerized using one of two LCUs (Valo® LED [standard power or extra- power mode] and OptiLux 501® QTH), with irradiation times set according to the manufacturer recommendations. Vickers microhardness was evaluated starting from the top to the bottom surface of each specimen. Ten measurements were made sequentially (0.4 mm intervals). A three-way ANOVA and Tukey’s post hoc test was used (significance of 0.05) to analyze the DOC data. Results: All resin composite groups cured with LED CLU (extra-power for 3 sec) and placed using a bulk-fill technique showed significant differences (p