An attempt was made to detect in QSO spectra lines of CO and CH molecu
le and CI(P-3(0) - P-3(1), lambda = 610 mu) fine-structure line, redsh
ifted to millimeter wavelengths. Five large and dense gas-dust complex
es discovered before in the optical range and, in some cases, in the 2
1-cm HI line, projected on the QSOs PKS 0528-250. PKS 1157 + 014. PKS
1229-021, PKS 0336-0142, PKS 0458-02, were studied. Upper limit on mol
ecular column density was obtained. In two cases - PKS 1157 + 014 and
PKS 1229-021 - weak emission lines were possible detected.