The polarization measurement of a nematic liquid crystal has been performed by a pyroelectric technique using short pulse of a Nd:YAG laser to create temperature increment. The temperature increment has been evaluated independently by monitoring temperature dependent birefringence for a He-Ne laser beam. The sign and absolute magnitude of surface polarization have been evaluated for both the planar and homeotropic orientation of the nematic liquid crystal at a solid substrate. The flexoelectric polarization in a hybrid cells has also been measured using the same pyroelectric technique. The value of the sum of the flexoelectric coefficients (e(1)+e(3)) for 5CB is negative and about - 13pC/m at room temperature.