We theoretically investigate the classical analogue of electromagnetically induced transparency (EIT) in a plasmonic structure constituted by double side cavities connected symmetrically to a waveguide. The EIT is demonstrated by simply detuning the sizes of the two cavities (i.e., the length difference ΔL, keeping their width w similar). The physical mechanism behind the EIT resonance is unveiled as being caused by the destructive and constructive interference between the confined modes in the two cavities. The former play the role of two coupled radiative oscillators. The proposed structure may have important applications for designing integrated devices such as: narrow-frequency optical filters, novel sensors and high-speed switches. © Springer International Publishing Switzerland 2016.