Skeletal isomerization of n-butane to isobutane was studied over HM, HZSM-5 and H-beta zeolites. The Lewis/Broensted ratio of acid sites was changed by vacuum treatment of the samples to 650 degrees C. gamma-Alumina and CoAlPO containing considerable portion of Lewis acid sites were also employed. It was found that the increased number of Lewis acid sites results in a substantial suppression of the n-butane conversion as well as selectivity to isobutane.