Summary: By now technologies, employing optical discharges find ever expanding applications in metering and diagnostic equipment in science, engineering and medicine. Based on the original experimental results authors look into some manifestations of spatial and temporal instabilities of the continuous and periodic pulse optical discharges (COD, POD). Set of the phenomena considered makes a great impact on a performance of laser produced plasmas essential for many applications, such as high brightness broadband light sources, for instance. Performance instability of continuous optical discharges followed by laser beam refraction on the refraction index gradients exhibit themselves first in spatial inhomogeneity of plasma thermal radiation luminosity and the other parameters related. Spatial inhomogeneity is accompanied by temporal instability of the plasma. The paper reports criteria for the appearance of instabilities related to the refraction followed by the limitations on supporting of elongated plasma. One of the main reasons of temporal instabilities of COD is thermal gravity convection. Instability of a heated gas zone surrounding optical discharge is followed by regular self-sustained oscillations leading in turn to pulsing of brightness and position of radiated plasma. Simple physical model proposed gives estimations correspondent to the observed pulse frequency dependence on gas pressure. In the case of periodic pulse optical discharges forced convection may be put forward as one of the main discharge instability reasons. Pulse optical discharge induces convective flows due to asymmetrical gas expanding following gasdynamic effect of the energy release zone shape determined by laser beam focusing system configuration.