Niobium‐selenium compounds in the composition range NbSe2&sngbnd;Nb1.14Se2can form layered crystals which are readily cleaved in a direction perpendicular to thecaxis. For compositions in the range NbSe2&sngbnd;Nb1.05Se2, two structures, a high‐temperature &zgr; phase and a lower‐temperature &egr; phase may be formed. Single crystals of &egr;‐NbSe2, &egr;‐Nb1.04Se2, &zgr;‐NbSe2, and &zgr;‐Nb1.04Se2were grown by the vapor transport technique and the optical absorption spectra of thin‐cleaved specimens in the visible and near infrared regions were studied. An infrared absorption spectrum to &lgr; = 15 &mgr; was also obtained for &egr;‐NbSe2. Accurate values of the absorption coefficient &agr; were measured at 10 nm intervals in the spectral region 400–620 nm. For all crystal types, &agr; was found to have peak value ∼4.5×105cm−1at &lgr; = 460 nm, decreasing steadily to ∼1.3× 105cm−1at &lgr; = 620 nm. The values of &agr; for &egr;‐NbSe2, along with bulk reflectivitiesR0measured on basal plane cleavage surfaces of opaque sections of &egr;‐NbSe2, have been used to calculate the optical constantsnandk. The most notable feature of the visible and near infrared studies is the similarity of the gross features of the absorption spectra of all four crystal types. This indicates that the absorption is governed principally by a mechanism operating largely within the Se&sngbnd;Nb&sngbnd;Se ``layer molecules'' and relatively independent of structure or the presence of interstitial excess metal. An absorption minimum centered about &lgr; = 1.2 &mgr; has been attributed to plasma oscillation of the conduction electrons, and calculations based on this assumption have yielded a valuem*≤5.9 m for the effective mass of these electrons.