tudy Objective*: To analyze the resin matrix monomer composition of selected bulk-fill and conventional resin-composite materials using reverse-phase liquid chromatography coupled with electron spray ionization mass spectrometry. *Method*: Six bulk-fill and eight conventional resin-composites were tested. Uncured resin-composites were analyzed using reverse-phase liquid chromatography/electron spray ionization mass spectrometry to assess resin composition and monomer amounts. *Results*: Detected main monomers included BisGMA, UDMA, TEGDMA, and BisEMA in varying combinations and amounts across different materials. Other monomers like HDDMA, DEGDMA, TCD-DI-HEA, and SDR-UDMA were also found in specific products. Positive correlation between logP values (hydrophobicity measure) and reverse-phase liquid chromatography retention time was observed.