The toxicity of cationic dendrimers is one of their most important drawbacks. Modification of the surface of those dendrimers is a way to obtain compounds that are tolerable by living organisms. However, the sole knowledge how such modifications influence the toxicity of dendrimers is not enough. It is also important to know how such modifications influence the ability of dendrimers to interact with biomolecules, as such interactions may be responsible for dendrimers fate in vivo. In this study the ability of poly(propylene imine) dendrimers of the fourth generation (G4 PPI) with surface modified with maltose moieties to interact with horse liver alcohol dehydrogenase (LADH) was examined. Fluorescence, room temperature tryptophan phosphorescence (RTTP), circular dichroism (CD), dynamic light scattering (DLS) and zeta potential measurements were applied to fully investigate those interactions. As a result, an ability of all studied G4 PPI dendrimers to interact with LADH was shown. However, the differences in the strength of influence of dendrimers on different parts of protein, depending on the dendrimer surface structure, were observed. All dendrimers increased flexibility of the core part of LADH to a similar degree. However, changes in LADH secondary structures upon the interaction with dendrimers depended on the type of the dendrimer. Additionally, experiments performed allowed us to propose the most probable part of LADH that is the subject of the structural changes as the cleft between catalytic and coenzyme binding subdomains of LADH.