The aim of this study was to evaluate by dispersive Raman spectroscopy the mineral and organic components of human dentin before and after laser irradiation and acid etching. The occlusal enamel of six non-carious human third molars was removed providing 6 dentin discs, which were divided in four quadrants each of them receiving a different surface treatment: etching with a 37% phosphoric acid gel (control); irradiation by Er:YAG laser (KaVo Key Laser II) with 80 mJ, 3 Hz, 30 s (group I); 120 mJ, 3 Hz, 30 s (group II); and 180 mJ, 3 Hz, 30 s (group III). The Raman spectra of normal (untreated) and treated dentin were analyzed and the mineral and the organic component were evaluated. Results were submitted to statistical analysis by ANOVA and Tukey's test at 5% significance level. The minerals and organic content were less affected in the control group and group I (p>0.05). Group II presented more reduction in mineral content (p<0.01) whereas in group III the inorganic (p<0.05) and organic (p<0.01) content were more affected. Dispersive Raman spectroscopy provided valid information of dentin chemical constituents with non-chemical sampling preparation.