The Raman spectra (3500 to 40 cm(-1)) of gaseous, liquid, and solid 3,3-difluoropropene, CH2CHCF2H, and the infrared spectra (3500 to 60 cm(-1)) of the gas and solid have been recorded. The spectra of the fluid phases are consistent with two stable conformers in equilibrium at ambient temperature. The mid-infrared spectra of the sample dissolved in liquid xenon as a function of temperature (-55 to -100 degrees C) have been recorded. Utilizing two conformer pairs, the enthalpy difference has been determined to be 82 +/- 10 cm(-1) (0.98 +/-0.12 kJ/mol) with the cis conformer (H atom of the difluoromethyl group is cis to the double bond) the more stable form. The cia conformer is also the more stable form in the liquid, and it is the only rotamer present in the solid. The first overtone of the asymmetric torsion for the cis conformer was observed at 179.6 cm(-1) with four successive excited-state overtones observed falling to lower frequency. The corresponding fundamental for the gauche conformer was observed at 97.65 cm(-1) with three excited states falling to lower frequency. Utilizing these torsional data along with the experimental enthalpy and gauche dihedral angle, the potential function governing the conformational interchange has been determined and the potential coefficients are V-1 = 215 +/- 16, V-2 = -111 +/- 17, V-3 = 633 +/- 6, V-4 = 54 +/- 8, V-5 = -25 +/- 4, and V-6 = -12 +/- 2 cm(-1.) The gauche to cis barrier is 560 cm(-1) (6.70 kJ/mol) and the gauche to gauche barrier is 744 cm(-1) (8.90 kJ/mol). The vibrational assignment for the 21 normal modes for the cis conformer is proposed and several of the fundamentals for the gauche conformer have been identified. The structural parameters, dipole moments, conformational stability, vibrational frequencies, infrared intensities, and Raman activities have been obtained from ab initio calculations, and the predicted conformational stability is consistent with the experimental results. These experimental and theoretical results are compared to the corresponding quantities of some similar molecules.