Breastfeeding has immense public health value for mothers, babies, and society. But there is an undesirably large gapbetween the number of new mothers who undertake and persist in breastfeeding compared to what would be a preferredlevel of accomplishment. This gap is a reflection of the many obstacles, both physical and psychological, that confront newmothers. Previous research has illuminated many of these concerns, but research on this problem is limited in part by theunavailability of a research instrument that can measure the key differences between first-time mothers and experiencedmothers, with regard to the challenges they face when breastfeeding and the instructional advice they require. Aninstrument was designed to measure motivational complexity associated with sustained breast feeding behaviour; theBreastfeeding Motivational Measurement Scale. It contains 51 self-report items (7 point Likert scale) that cluster into fourcategories related to perceived value of breast-feeding, confidence to succeed, factors that influence success or failure, andstrength of intentions, or goal. However, this scale has not been validated in terms of its sensitivity to profile the motivationof new mothers and experienced mothers. This issue was investigated by having 202 breastfeeding mothers (100 first timemothers) fill out the scale. The analysis reported in this paper is a three factor solution consisting of value, midwife support,and expectancies for success that explained the characteristics of first time mothers as a known group. These resultssupport the validity of the BMM scale as a diagnostic tool for research on first time mothers who are learning to breastfeed.Further research studies are required to further test the validity of the scale in additional subgroups.