In this work, results are presented concerning the synthesis and characterization (FTIR, H-1-NMR, C-13-NMR) of two bromine containing monomers: 2-(2-bromoisobutyryloxy) ethyl methacrylate (BIEM) and 2-( 2-bromopropionyloxy) ethyl methacrylate (BPEM). The synthesis of these monomers has been made with the aim to use them as radio-opaque agents in the composition of PMMA-based bone cements. Copolymers were synthesized by free radical polymerization, using methyl methacrylate ( MMA) and one of the bromine containing monomers in different concentrations. Copolymerizations were carried out directly in the thermostatic cell of an NMR spectrometer using deuterated benzene as solvent. The reactivity ratios of the copolymerization systems were determined by H-1-NMR analysis.