Despite the great attention on the factors affecting the radical addition efficiency onto a double bond, the solvent influence remains largely unknown and the subject of discussions. In this Letter, the influence of the solvent is examined both experimentally (by use of a well adapted radical) and by quantum mechanical calculations associated with continuum solvation models. The combination of experimental measurements and theoretical results in this work shows that the solvent polarity represents indeed an important factor affecting the addition reaction. The validity of conclusions obtained by previous calculations carried out in gas phase is also reexamined. (c) 2005 Elsevier B.V. All rights reserved.