The inhibition potentials of two pyridazine derivatives 5-benzyl-6-methyl pyridazine-3-thione (BMPT) and 5-benzyl- 6-methyl pyridazine-3-one(BMPO) has been elucidated using quantum chemical calculations based on density functional theory (DFT) at the B3LYP/6-31G(d,P) basis set level in order to investigate the relationship between their molecular and electronic structure and inhibition efficiency. The quantum chemical properties such as EHOMO (highest occupied molecular orbital energy), ELUMO (lowest unoccupied molecular orbital energy), energy gap (ΔE), dipole moment (μ), hardness (η), softness (S), the absolute electronegativity (χ), the fractions of electrons transferred (ΔN) and the electrophilicity index (ω) were calculated. The local reactivity has been analyzed through the Fukui function and condensed softness indices in order to compare the possible sites for nucleophilic and electrophilic attacks. The obtained theoretical data agree well with the experimental results.