Three activated carbons exhibiting different textural characteristics were considered as support for CuBr-HMTETA catalyst in the Atom Transfer Radical Polymerization (ATRP) of methyl methacrylate. The pore distribution of the activated carbons played an important role in the control of the polymerization reaction: polydispersity index always failed in the range 1.1-1.3. However, the accessibility of the catalyst to pores in the activated carbon was limited by pore size and growing polymer size. Catalyst located within the micropores of spherical carbon was isolated from the growing polymer chains during the polymerization reaction, which took place at the mesopores. Mesoporous structure of LMA F-12 carbon enhanced polymerization rate but control over the molecular weight distribution was decreased. A carbon with an adequate distribution of micro- and mesoporosity (RGC-30) provided a suitable balance between activation and deactivation processes involving Cu((I)) and Cu((II)) catalytic species, which resulted in the appropriate control of the molecular weight during the methyl methacrylate polymerization reaction. (C) 2009 Elsevier B.V. All rights reserved.