OBJECTIVES: To compare the total value of payer's expenditures on Nutramigen LGG 1, Nutramigen LGG 2, Neocate LCP, Neocate Advance in patients with allergy to cow's milk protein estimated in the manufacturers’ Budget Impact Analyses (BIAs) submitted with the reimbursement applications to AOTMiT  and actual expenditures of the National Health Fund (NHF). METHODS: Annual public payer’s expenditures estimated in manufacturers’ BIAs for Nutramigen LGG 1/2, Neocate LCP/Advance and actual expenditures reported by the NHF were compared. RSSs were not taken into account. Analysed drugs were chosen on the basis of the same indication. Actual expenditures and number of package were taken from the financial reports of the NHF for the first and second year of the reimbursement for each drug. RESULTS: For drugs Nutramigen LGG1/2 and Neocate LCP/Advance in patients with allergy to cow's milk protein, the sum of total expenditures estimated in BIA submitted with the reimbursement applications was 55,158 million PLN in the first year and 57,637 million PLN in the second year, and they were higher than the actual expenditures reported by the NHF: 5,3 million PLN and 16,14 million PLN, respectively. The expenditures estimated in BIAs were overestimated by 939% in the first year of the reimbursement and 257% in the second year of reimbursement. The number of packages of the Nutramigen LGG 1/2, Neocate LCP/Advance also were analysed. The number of reimbursed packages estimated in BIAs in comparison to its actual number from the NHF reports was overestimated by 2029% in the first year and 492% in the second year of reimbursement. CONCLUSIONS: In the case of drugs chosen for this analysis, total payer's expenditures estimated in BIAs submitted with the reimbursement applications were overestimated in comparison to the real life expenditures of the NHF in Poland.