To evaluate the quasistatic parameters of arbitrary coplanar waveguide (CPW) structures, a new numerical approach based on the combination of the conformal mapping technique and the finite-difference method is presented. The validity and versatility of the proposed method have been demonstrated by application in thr ee kinds of CPWs: 1) with conductor backing, 2) with finite-extent substrate, and 3) with an enclosed shielding box. Compared with the data published in the literature, the numerical results of this method show very good agreement. (C) 1997 John Wiley & Sons, Inc.