Purpose: of this study was to evaluate the influence of LCU type on temperature changes during polymerization of two resin-based composites with different matrices (silorane-based and methacrylate-based). Design/methodology/approach: The light-curing units (LCUs) selected for this study included three various LEDs (LED 55, LED 10W and Radii Plus) and a QTH (Elipar Highlight). Two different resin-based composites (RBCs) were used in this study. The silorane-based composite Filtek Silorane and methacrylate-based composite Filtek P60. Temperature changes were measured during polymerization with LCUs working in various curing modes. Empty mold, Filtek Silorane RBC and Filtek P60 RBC were cured from a distance of 0 mm, 2.5 mm and 5 mm. Findings: Regardless the type of RBC, every time the highest temperature was reached with LED 55 light-curing unit. Comparing Filtek Silorane and Filtek P60 RBCs, the temperature of Filtek Silorane RBC was significantly higher with LED 55 (35.4±4.9), Radii Plus (33.5±5.5) and Elipar Highlight LCUs (31.2±3.1), and significantly lower with LED 10W LCU (28.5±7.5). For Filtek P60 the measured temperatures of polymerization were 32.7±3.2 for LED 55 LCU, 29.9±5.6 for LED 10W LCU, 31.0±2.4 for RadiiPlus LCU and 30.2±1.8 for Elipar Highlight LCU. Research limitations/implications: The research was carried out for two groups of composite materials used for teeth restoration in modern dentistry. The experiment should be repeated on a broader group of resin-based composite dental materials and should take into account more light-curing units. The study could be also done in situ on a real tooth model. Practical implications: This research gives an insight into the range of temperatures that are generated during polymerization process of dental composite materials. The results of the study are of a great value during choosing the restorative composite material for particular application in the oral cavity, selecting the right light-curing-unit and adjusting the curing parameters Originality/value: The results of the study allow to conclude that the temperature values vary for each resin-based material, according to light-curing-unit type and the distance of curing seemed to have least influence on temperature changes during polymerization.