  We have searched for molecular absorption lines at millimeter wavelengths in
eleven gravitational lens systems discovered in the JVAS/CLASS surveys of flat
spectrum radio sources. Spectra of only one source 1030+074 were obtained in
the 3-, 2- and 1.3-millimeter band at the frequencies corresponding to common
molecular transitions of CO and HCO+ as continuum emission was not found in any
of the other sources. We calculated upper limits to the column density in
molecular absorption for 1030+074, using an excitation temperature of 15 K, to
be N_{CO} < 6.3 x 10^{13} cm^{-2} and N_{HCO+} < 1.3 x 10^{11} cm^{-2},
equivalent to hydrogen column density of the order N_H < 10^{18} cm^{-2},
assuming standard molecular abundances. We also present the best upper limits
of the continuum at the lower frequency for the other 10 gravitational lenses.
