A distance measure based on the line spectrum pair (LSP) representation is proposed for improving the performance of speech recognition systems. The quefrency weighted cepstrum is to the root-power sum (RPS) of the inverse filter what the proposed measure is to the RPS of the filter whose roots are on the unit circle and expressed as LSP frequencies. The recognition results on a set of 10 confusable syllables show that the performance of this measure is better than that of the Euclidean distance measure for the LSP.