Chitosan functionalized with 2-pyridinecarboxaldehyde and 4-pyridinecarboxaldehyde were used to study the equilibrium constants of adsorption copper(II) in aqueous solutions. The degree of substitution of NH2 groups of the chitosan was 0.85. The adsorption parameters K (adsorption constants Langmuir) and {R-T} (maximum value of adsorbed copper(II) ions) were calculated using Langmuir＇s equations by non-linear regression methods. The K-L (equilibrium adsorption constant) and {R-T} values for N-(2-pyridyl-methyl)chitosan systems were higher than those for N-(4-pyridyl-methyl)chitosan. The difference is related to the nitrogen position at the pyridine ring, since the degree of substitution is the same in the two polymers.