The present paper is devoted to the synthesis and textural characterization of silica materials. The mixed silica sample was composed of Si-100 silica gel with small agglomerates of MCM41 molecular sieve deposited on its surface. MCM41 mesoporous silicates were synthesized using octadecyl trimethylammonium bromide. Using a new synthesis procedure it was possible to prepare silica containing three groups of mesopores. The recently developed positronium annihilation lifetime spectroscopy method for characterization of mesoporous materials was applied ro the investigated silica materials. The results were compared with those from the nitrogen desorption method. The current studies demonstrate moderate consistency of pore size characteristics obtained by using various techniques.