Breastfeeding provide many good impacts on health and economics side. This study tries toestimate the economic impact of not breastfeeding due to diarrhea and PRD cases in NorthSumatera. The economic impact elaborated by finds health system medical cost and thepatient/non- medical cost. This paper calculates health system medical cost from publichospital, private hospital, and primary health center while the patient cost calculated from135 patients in 3 kinds of health facilities. This paper combines primary data with CensusData 2010 and IDHS 2012 to get total cost of not breastfeeding in North Sumatera. Thecosting process shows there are economic loss about US$1,290,582 with average cost aboutUS$ 13.48 in North Sumatera. The total cost consist of health system perspective costabout US$ 799,050 and patient costs about 491,532. This show that most of the cost comesfrom the health system cost/medical cost about 61.91% and the 38.09% borne from thepatient costs and non-medical cost