This study present the effect of model-plant mismatch on MPC controller performance for set-point tracking. The methodology of this study is based on the analysis of closed loop data from the process. Four types of mismatch has been investigated: (1) gain mismatch, (2) reverse gain mismatch, (3) time constant mismatch and (4) time delay mismatch are illustrated to a case study of Wood and Berry distillation column. This study shows that the gain mismatch has significant effect on MPC controller performance compared to time constant and time delay mismatch. For set-point tracking, MPC controller performance is bad in the presence of gain mismatch but it is good in the presence of time constant and time delay mismatch © 2011 Asian Network for Scientific Information.