Density, rho, and speed of sound, u, were measured for two binary mixtures, 1-ethyl-3-methylimidazolium tetrafluoroborate (1) + N,N-dimethylformamide (2) and 1-ethyl-3-methylimidazolium tetrafluoroborate (1) + N,N-dimethylacetamide (2), over the entire range of compositions at T = 293.15-343.15 K in 5 K intervals using an Anton Paar density and sound velocity analyzer (DSA 5000). Also excess molar volume, V-m(E) isentropic compressibility, k(s), and isentropic compressibility deviation, Delta k(s) were calculated. For these two binary mixtures, the V-m(E), values were negative in x(1) = 0.1-0.8, they were positive in x(1) >= 0.8, and they became more negative with increase in the temperature from 293.15 to 343.15 K. For both systems, the most negative VI values were observed in the region of x(1) = 0.5. The V-m(E)!, values were fitted to the Redlich-Kister polynomial equation. The perturbed chain statistical associating fluid theory (PC-SAFT) was also employed in order to correlate the densities of the binary mixtures at the temperature range of 293.15-343.15 K. The results obtained were in good agreement with the experimental data.