Evidence of the existence of noise-sustained patterns in nonlinear optical systems is given. They are found in passive optical cavities, filled by Kerr type nonlinear media, when the angle of incidence of the pump beam is not zero, in a regime of convective instability. These patterns arise as a macroscopic manifestation of amplified noise. We characterize the difference between noise-sustained and deterministic patterns in terms of statistical properties of the field spectral intensity.