Fluorescence and excitation spectra and fluorescence lifetimes have been measured for alpha,omega-dithienylbutadiene (DTB) and alpha,omega-dithienylethylene (DTE) in a jet-cooled He expansion and in the static vapor phase. It is shown that the emission of DTB in the static vapor phase consists of the S-1(2(1)A(g)) and S-2(1(1)B(u)) fluorescence, while the emission in a jet consists of solely the S-1 fluorescence. The fluorescence quantum yields of DTB and DTE vapors decrease significantly with increasing excitation energy. The conformer-specific fluorescence was measured for DTB and DTE in a jet. The false S-1 (2(1)A(g)) origin of the most stable conformer of DTB was observed at 25470.5 cm(-1) in a jet, which is located approximately 2800 cm(-1) below the S-2 (1(1)B(u)) origin. The S-1 origins of the two conformers of DTE were observed at 28648 and 28966 cm(-1) in a jet, and the S-1 state of the most stable conformer is assigned as 1(1)B(u).