This work reports on the thermal diffusivity of the SiO2-Na2CO3-B2O3-Al2O3 (SNAB) glass system doped with semiconductor nanocrystals of CdS and Nd3+ ions. Thermal diffusivity (D) was obtained by the Thermal Lens technique. It is shown that D decreases up to 30% when SNAB is doped with CdS nanocrystals. The effect is discussed in terms of heat transport by phonons as well as interface and surface scattering. (C) 2011 Elsevier B. V. All rights reserved.