We fabricated two dimensional photonic crystal structures in zinc oxide films with focused ion beam etching. Lasing is realized in the near ultraviolet frequency at room temperature under optical pumping. From the measurement of lasing frequency and spatial profile of the lasing modes, as well as the photonic band structure calculation, we conclude that lasing occurs in either localized or extended defect modes near the dielectric edge of photonic band gap. These defect modes originate from the structure disorder unintentionally introduced during the fabrication process. Fine tuning of lasing wavelength across 20nm range has been realized by varying the lattice constant of PhCS structure. A qualitative explanation for these PhCS lasers with self optimization of laser cavity quality factor has been proposed.