Optical parametric oscillators emit light with non-classical correlations between opposite spatial modes (twin beams). We consider these devices in presence of an intracavity photonic crystal, modeled by a spatial modulation of the refractive index. The introduction of photonic crystals allows to control not only the macroscopic transverse profile of the emitted light beam but also its quantum fluctuations. We employ the Q representation to study pump and signal spatial correlations.