Aims.Our goal is to characterize AGN populations by comparing their X-ray and optical classifications within the framework of the standard orientation-based unified scheme. Methods: We present a sample of 99 spectroscopically identified (R =3sigma) in the [ 2-10] keV band with fluxes between 8 × 10[SUP]-15[/SUP] and 8 × 10[SUP]-14[/SUP] erg s[SUP]-1[/SUP] cm[SUP]-2[/SUP], and which have more than 80 counts. We have compared their X-ray and optical classifications. To this end, we performed an X-ray spectral analysis for all of these 99 X-ray sources in order to assess whether they are intrinsically absorbed or not. The X-ray classification is based on the measured intrinsic column density. The optical classification is based on the measured FWHM of the permitted emission lines, the absence of broad lines being due to obscuration within the framework of the standard AGN unified scheme. Results: Introducing the fourfold point correlation coefficient r, we find a mild correlation between the X-ray and the optical classifications (r = 0.28), as up to 32 X-ray sources out of 99 have differing X-ray and optical classifications: on one hand, 10% of the type 1 sources (7/32) present broad emission lines in their optical spectra and strong absorption (N{H}[SUP]int[/SUP] >= 10[SUP]22[/SUP] cm[SUP]-2[/SUP]) in the X-rays. These objects are highly luminous AGN lying at high redshift and thus dilution effects by the host galaxy light are totally ruled out, their discrepant nature being an intrinsic property instead. Their X-ray luminosities and redshifts distributions are consistent with those of the unabsorbed X-ray sources with broad emission lines (L{2-10} 4 × 10[SUP]44[/SUP] erg s[SUP]-1[/SUP]; z 1.9). On the other hand, 25/32 are moderate luminosity (L{2-10}