Osteoporosis is a generalized disease of the skeleton, characterized by low bone mineral density and disturbance of microarchitecture, leading to a lower mechanical endurance of bones and enlargements of susceptibility to fractures. One of the most significant features leading to osteoporosis is treatment with AED. Epilepsy usually reveals at young and needs long treatment. For the early diagnosis of osteoporosis the most important is estimation of real reduction of bone mineral density (BMD). Nowadays the most popular diagnostic method is dual energy X-ray absorptiometry (DEXA). Yet it reveals advanced level of osteoporosis, which cannot be reversed. Thus there is a need for diagnosis development of new markers of bone metabolism: markers of bone formation and bone resorption. The studies were conducted in group 100 patients aged 20-50 treated over 2 years with AED and in the control group – 40 persons properly chosen in respect to age and sex. The patients were examined by DEXA and bone markers: CTX (collagen type and cross-linked C-telopeptide) and oste-ocalcin. The persons suffering from other diseases or intaking different speciments affecting bone metabolism were eliminate from both groups. Results: Long-term intake AED considerably affects the decrease of BMD. It takes only few years of AED intake for the patients to develop osteopenia or osteoporosis. CTX is the most sensitive marker in patients treated below 6 years, while DEXA is most sensitive in patients treated longer than 6 years. The biggest changes in bone metabolism were found in patients treated with phenytoin.