An approximate and accurate enough multi-conductor transmission line model is developed for analysis of side-coupled metal-insulator-metal (MINI) waveguicles MIM waveguides have been already modeled by single conductor transmission lines. Here, the side coupling effects that exist between neighboring plasmonic structures are taken into account by finding appropriate values for distributed mutual inductance and mutual capacitance between every two neighboring conductors in the conventional single conductor transmission line models. In this manner, multi conductor transmission line models are introduced. Closed form expressions are given for the transmission and reflection of miscellaneous MIM plasmonic structures, e.g. dual-stop-band and band-pass filters. In all examples, the results of the proposed model are compared against the fully numerical finite difference time domain (FDTD) method. The results of the analytical model are in good agreement with the numerical results. (C) 2013 Elsevier B.V. All rights reserved.