Molar-mass distributions (MMDs) of asphaltenes with two inhibitors have been characterized by experimental and computer calculations; experimental data of the asphaltene molecular weight were obtained from gel permeation chromatography (GPC) and compared to experimental data from vapor pressure osmometry (VPO). The MMD experimental behaviors were obtained using GPC to three systems: asphaltene + toluene, asphaltene + toluene + 4-nonylphenol inhibitor, and asphaltene + toluene + M2 inhibitor. Besides, a molecular model of particle agglomeration control (PAC) was used to obtain tendencies of MMD in the presence of a dispersant at different conditions. Theoretical and experimental analyses presented here provide an understanding of the behavior of the asphaltenes from crude oil with two inhibitors. An anomalous effect of the asphaltene agglomeration with respect to the asphaltene concentration was found and validated using the PAC model. It has been found that the inhibitor efficiency depends upon concentration levels of the asphaltenes and inhibitors.