The book provides a general introduction to advanced computational techniques applied in various stages of drug discovery. In particular, it focuses on molecular modeling, ligand- and structure-based drug design methods, and data mining in chemical informatics. Application side of this book deals with the development of the first structure-based three-dimensional quantitative structure-activity relationship (3D-QSAR) model of butyrylcholinesterase - a putative drug target for the treatment of Alzheimer''s disease. The other part is comprised of detailed work conducted on 5-HT2C agonists. It describes pharmacophore modeling and 3D-QSAR studies. Comparative Molecular Field Analysis coupled with a genetic algorithm (CoMFA-GA) was carried out for aligned ligands. The last part describes the drug target MTB-Thymidine monophosphate kinase (TMPKMtub). The molecular modeling analyses resulted in identification of a cluster of water molecules that mediate key interactions between bound ligands and backbone atoms of the enzyme residues.