OBJECTIVES: To compare the total value of payer's expenditures on Cimzia (certolizumab pegol) and RoActemra (tocilizumab) in patients with severe rheumatoid arthritis 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 Cimzia and RoActemra 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 and financing through the same therapeutic programme in Poland. Actual expenditures and population size were taken from the financial reports of the NHF for the first and second year (actual data on 11 months for expenditures were extrapolated to one year) of reimbursement for each drug. RESULTS: For drugs Cimzia and RoActemra in patients with severe rheumatoid arthritis, the sum of total expenditures estimated in BIAs submitted with  the reimbursement applications was 18,04 million PLN in the first year and 28,47 million PLN in the second year, and they were lower than the actual expenditures reported by the NHF: 20,03 million PLN and 36,51 million PLN, respectively. The expenditures estimated in BIAs were underestimated by 10% in the first year of reimbursement and 22% in the second year of reimbursement. Population size estimated in BIAs in comparison to its actual size from the NHF reports was underestimated by 61% in the first year and 57% 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 underestimated in comparison to the real life expenditures of the NHF in Poland.