Periodic noises are unwished and spurious signals that create repetitive pattern on images and decreased the visual quality. Firstly, this paper investigates various methods for reducing the effects of the periodic noise in digital images. Then an adaptive optimum notch filter is proposed. In the proposed method, the regions of noise frequencies are determined by analyzing the spectral of noisy image. Then, the repetitive pattern of the periodic noise is produced by applying the corresponding notch pass filter. Finally, an output image with reduced periodic noise is restored by an optimum notch filter method. The results of the proposed adaptive optimum notch filter are compared by the mean and the median filtering techniques in frequency domain. The results show that the proposed filter has higher performances, visually and statistically, and has lower computational cost. In spite of the other compared methods, the proposed filter does not need to tune any parameters.