Euroskyrad (ESR) is a network of European groups that focus their research on the atmospheric aerosols by applying the Skyrad inversion algorithm indistinctly to Cimel CE318 and Prede POM sky - sun radiometers. This study addresses the performance of ESR new algorithms in comparison to AERONET for aerosol optical depth retrieval from direct sun measurements. More specifically, we have applied the ESR algorithms (ESR.pack, modes 1 and 2) to a Cimel CE318 and Prede POM-01L simultaneous database obtained at Valencia (Spain) and compared the resultant aerosol optical depth with the AERONET retrievals. The results obtained with Cimel agree with AERONET within 0,009 - 0,011 and 0,001 - 0,007 (ESR modes 1 and 2, respectively) depending on wavelength. Furthermore, a comparison between aerosol optical depth obtained from Cimel and Prede radiometers is also possible by using the same code, and the results agree better than 0,003 - 0,006 independently of ESR mode. Finally, the comparison of AOD obtained with Prede/ESR against Cimel/AERONET shows a reasonable deviation for mode 1 (0,006 - 0,012) and a very good agreement for mode 2 (0,004 - 0,007). In general these differences fall within the nominal AERONET uncertainty of 0.01-0.02 for field instruments.