We consider cognitive processes and their impact on the performance of cognitive radio networks (CRN). We model the cognition cycle, the main control process of the cognitive radio (CR), during which CR sequentially senses and estimates the environment state, creates plans based on the knowledge (models) of itself and that of the environment, makes decisions in order to optimize certain objectives and then acts. The proposed framework is analyzed and the performance of the CRN is evaluated. We show the impact of the sensing rate and the system dynamics on the waiting times of secondary users. Then model-based analysis is also used to solve control and decision making tasks, which actually gives the radio its “cognitive” ability. Particularly, we design an efficient strategy for accessing the vacant spectrum bands and managing the transmission-sampling trade-off.