Introduction:
Scientific studies on herbal medicinal products, including randomized controlled trials, are being conducted worldwide. At the time of evidence based medicine, the quality and standardization of research is still elevated to the a higher level. One of the important reasons for such a situation is publication of the relevant guidelines by international organizations, such as the WHO.

Objective:
Analysis of methodological differences in research on herbal medicinal products.

Material and Methods:
Review of available literature concerning methodological differences in research on herbal medicinal products, including European Union documents and the WHO guidelines.

Results:
The above-mentioned methodological differences apply to all stages – from cultivation of herbal medicinal product through its preliminary processing to obtaining final standardized product, also the construction of research protocol and selection of population into the control and experimental groups. In the case of herbal medicinal products, there are also more numerous environmental, social and cultural interactions than in the case of research on synthetic substances.

Conclusions:
Conclusions drawn from clinical studies are one of the pillars of modern medicine; however, these studies must be properly conducted to enable proper interpretation. Conducting clinical trials on herbal medicinal products may make herbal therapy a fully-fledged branch of medicine, and the knowledge obtained from these studies may facilitate making clinical decisions.