Nayif A Jado EngineerABSTRUCT Aims: The aim of this study was to investigate the effect of storage time (immediately after polymerization and after one month of artificial saliva storage) on the degree of conversion (DC) of restorative type of light cured dental materials. Materials and Methods: Sixty samples of polyethylene molds were prepared. The samples were divided into three groups each of 20. The first group was filled with Composite resin, second group was filled with Compomer and the third group was filled with Resin modified glass ionomer cement (RMGIC). Each group was subdivided into two subgroups; each of ten according to storage time: The DC was tested for the first subgroup immediately after polymerization, while the DC of the second subgroup was tested after one month of storage in artificial saliva. The DC was investigated by Fourier-transform infrared spectroscopy (FTIR). Results: ANOVA test was used for statistical analysis. The results showed that there was a significant difference (p<0.05) in DC between the subgroups tested immediately after polymerization and the subgroups tested after one month of artificial saliva storage for Composite resin and Compomer. While RMGIC showed no significant difference (p>0.05) in DC between the subgroup tested immediately after polymerization and the subgroups tested after one month of artificial saliva storage. Conclusions: One month storage time has an effect on the DC of Composite and Compomer, but it has no effect on the DC of RMGIC.