A dual-level interpolation approach for constructing potential energy surfaces is investigated through constructing a surface for describing H2CN -> H + HCN dissociation. The basic idea of the approach is to construct a reference surface by interpolating a set of lower-level ab initio points so as to reduce the number of high-level points needed for generating the final surface. The local interpolating moving least-squares (L-IMLS) method is employed as the interpolating tool, and its accuracy and efficiency are further investigated. It is shown that the number of high-level points required to achieve a given accuracy is greatly reduced by using the dual-level approach. (C) 2008 Elsevier B.V. All rights reserved.