The objective of this work was to characterize the fractionation of Photosynthetically Active Radiation (PAR) and its interaction with the vegetation cover of a portion of Seasonally Dry Tropical Forest at the end of the rainy season in Northeast Brazil. The leaf area index was correlated with each component of the PAR radiation balance to find the best fit models. Second-order polynomial models were used to identify the relationship between the PAR components and the LAI. It was observed that the fractionation of the PAR radiation reflected, absorbed, transmitted, and reflected by the soil and absorbed by the canopy varied according to the class of use and vegetation cover. Besides, as the density of vegetation increased, there was a decrease in the PAR transmitted and reflected, and an increase in the PAR absorbed and, in the PAR, reflected by the soil and absorbed by the canopy, on all the analyzed dates. It was also found that vegetated areas showed greater use of PAR radiation compared to other areas such as urban infrastructure. The vegetation of the São Francisco Valley has great heterogeneity and, consequently, there is a complex relationship with the distribution of photosynthetically active radiation on the surface.