We address the problem of license plate detection in video surveillance systems. The Adaboost based approach, known for relative ease of implementation, makes use of discriminative features such as edges or Haar-like features. In this paper, we propose a novel detection algorithm based on local structure patterns for license plate detection. The proposed algorithm includes post-processing methods to reduce false positive rate using positional and color information of license plates. Experimental results demonstrate effectiveness of the proposed method compared to both the edge and Haar-like feature based methods.