A semi-lumped Composite Right/Left-Handed (CRLH) equivalent circuit is proposed and analysed, then a CRLH design method is presented. This equivalent circuit use a transmission line which replace the inductance of the series resonator from the fully lumped CRLH equivalent circuit, but also contains a parallel lumped resonator. A CRLH structure is designed following the proposed method and then it is analysed numerically. It is shown the results are in very good agreement with the expected ones.