We investigated difference of the individual average glandular dose (AGD) as individual patient dose between digital and screen-film mammography systems. The difference was analyzed for every individual breast thickness or breast density. AGD that is average radiation absorbed dose to glandular breast tissue is accepted as an estimation of the patient dose in mammography. If calculating the individual AGD, Glandular Rate, which is the rate of the quantity of glandular tissues to breast, should be known for each patient. Then, we built an estimating system of individual glandular rate from each clinical mammogram by using breast tissue equivalent phantoms that are able to change the mixture ratio of adipose and glandular tissue and the thickness. Two data sets of Cranial- Caudal view mammograms were estimated. The one is 100 images from 50 patients by the screen-film (min-R 2000, kodak), and the another is 49 images from 25 patients by computed radiography (CR, Fuji) system. AGDs of screen-film and CR systems were 1.6mGy and 2.0mGy, respectively. The increase of AGD showed the plus correlation with breast thickness.