  In this poster we show our preliminary analysis of DIBs (Diffuse Interstellar
Bands) and other interstellar absorption lines with the purpose of
understanding their origin and their relationship with extinction. We use the
biggest Galactic O-star blue-violet spectroscopic sample ever (GOSSS, see
contribution by Ma\'iz Apell\'aniz at this meeting). This sample allows a new
insight on this topic because of the adequacy of O-star spectra, the sample
number (700 and increasing, 400 used here), and their distribution in the MW
disk. We confirm the high correlation coefficients between different DIBs and
E(B - V), though the detailed behavior of each case shows small differences. We
also detect a moderately low correlation coefficient between Ca II
{\lambda}3934 (Ca K) and E(B - V) with a peculiar spatial distribution that we
ascribe to the relationship between line saturation and velocity profiles for
Ca II {\lambda}3934.
