Viruses have important role in nature because they infect different hosts. Since they are obligatory intracellular parasites, they cause various diseases and stimulate changes in living cells that can also play an important role in evolution. Considering there are many different types of viruses with different structures and biological characteristics, a large number of diagnostic tests are required for their successful diagnostic. Not all approaches are applicable to all viral diseases, so it is important to know which method to choose and when to apply it. Viral nucleic acids or proteins can be detected by molecular methods. They are specific and sensitive, which means that virus presence can be detected in a sample with its' very low concentration. Molecular methods are usually based on the amplification of parts of the viral genome by different types of polymerase chain reactions, electrophoretic analysis of the obtained DNA or viral protein molecules, and detection of the viral genome using hybridization techniques. On the other hand, serological methods, based on the reaction of antigens and antibodies, are used to detect virus antigens and specific antibodies generated as a result of infection and give rapid results. There are different serological methods, suchprecipitation techniques, as single and double radial diffusion, immunohistological methods that detect antigen in infected tissues, frequently used immunoenzyme assays such as ELISA and many other. It is necessary to have a good understanding of each method to ensure the accurate and reliable application of diagnostic methods, which is prerequisite for adequate and timely medical treatment.