This book is the proceedings of Third International Conference on Computational Science, Engineering and Information Technology (CCSEIT-2013) that was held in Konya, Turkey, on June 7-9. CCSEIT-2013 provided an excellent international forum for sharing knowledge and results in theory, methodology and applications of computational science, engineering and information technology. This book contains research results, projects, survey work and industrial experiences representing significant advances in the field. The different contributions collected in this book cover five main areas: algorithms, data structures and applications;  wireless and mobile networks; computer networks and communications; natural language processing and information theory; cryptography and information security.  .