— This paper presents an object active visual search behavior in a 3D environment performed by a HRP-2 humanoid robot. The search is formalized as an optimization problem in which the goal is to maximize the target detection probability while minimizing the energy/distance and time to achieve the task. Natural constraints on the camera parameter space based on the characteristics of the recognition system are used to reduce the dimension of the problem and to speed up the optimization process to achieve a real time behavior. We present simulation and real experimental results using an HRP-2 robot.