In the present work the properties of Cartan subalgebras and their connection with regular elements in finite-dimensional Lie algebras are extended to the case of Leibniz algebras. It is shown that Cartan subalgebras and regular elements of a Leibniz algebra correspond to Cartan subalgebras and regular elements of a Lie algebra by a natural homomorphism. Conjugacy of Cartan subalgebras of Leibniz algebras is shown. (c) 2006 Elsevier Inc. All rights reserved.