The International Conference on Mathematics and Computer Science 2009 (ICMCS 2009) intends to assemble researchers and scientists from Mathematics and Computer Science, covering topics common to both areas. This 3rd International conference aims at creating a forum for researchers working on applications of Mathematics in Computer Science. On the one hand, mathematicians found a new source of difficult and interesting questions in the analysis of models for Computer Science. On the other hand, the analysis of algorithms and data structures experienced significant developments with the use of existing tools. It provides excellent opportunity to the researchers, academicians and scientists for discussion of topics at the intersecting domain of mathematics and computer science.