Milk adulteration is an international social problem. Consumption of adulterated milk may cause serious health problems and a great concern of the food industry has been raised. In this study, a method based on the polymerase chain reaction (PCR) principle was validated for detecting cow’s milk in goat's dairy products. A total of 40 goat's dairy products commonly consumed in Greece, were tested. Various concentrations, from 0.01 to 90%, of cows’ milk in goats’ milk samples were prepared for DNA extraction and further PCR analysis. Selection of highly polymorphic regions within the cow and goat mitochondrial D-loops, showing low homology between the two species, allowed to choose specific primer pairs for detection of cow and goat DNA. After electrophoresis, cow DNA was characterised by the fragment of the size of 300 bp, goat DNA by the fragment of 444 bp. The detection limit of the PCR method was 0.01% while sensitivity and specificity of the method were both 100%. Goat dairy products samples were tested for the presence of cow DNA. Thirty six out of forty (90%) that were tested, were found to produce cow-specific PCR product in addition to goat PCR product while only two samples gave goat-specific product only. The results are disappointing in terms of the food labelling honesty but on the other hand PCR is again a quickly, easy and reliable method that could be used for extended adulteration screening.