Considering the importance of mangroves for the coastal zone, its characterization, conservation, and monitoring become crucial. The use of remote sensing techniques for the measurement, monitoring, and reporting of structure, biomass,9–11 and carbon stocks in forests seems to be a valuable and low-cost tool when compared to field survey.12,13 Different techniques and data are used to detect mangrove-forest changes, species diversity, structural characterization, biomass estimation, mapping, quantifying, and qualifying mangrove forests using optical imagery,14–16 light detection and range data,17–19 and synthetic aperture radar (SAR) imagery. SAR data have been used mainly for mapping mangrove area, biomass estimations, and structural analysis of mangrove forests.20–27 SAR is an active microwave sensor that allows the penetration of the incident signal through the forest canopy. The penetration and interaction of the incident signal and the intensity of the backscattered signal is dependent on the characteristics of the SAR sensor itself, in terms of its frequency or wavelength, polarization, and incidence angle as well as on the parameters of the studied target, such as its dielectric constant, rugosity, and geometry. The penetration of the SAR microwaves through the canopy is dependent on these characteristics, and when it occurs, it allows information about the vegetation structure of mangrove forests to be obtained. C-band SAR pulses interact mainly with the leaves and the superficial crown of the tree, while the L-band interaction occurs on the canopy, leaves, branches, trunks, and trunks–ground interaction. The backscattered signal from the forest includes components of many scattering mechanisms, such as scattering of the canopy, volumetric scattering, double-bounce, superficial scattering, and interaction with the ground and trunks.28 The forest backscatter also varies according to soil moisture, as in the case of wetlands like mangroves. The backscatter increases due to the interaction between the flooded soil and trunks, resulting in the double bounce scattering.29,30 SAR imaging in P- and L-bands is more susceptible to variations in mangrove biomass.21,24 Spaceborne X- and C-band SAR sensors, together with other optical sensors have been available to provide data for observing and quantifying changes in mangroves.18,19,22,27 However, the L-band SAR has a relatively better capacity to support mangrove monitoring efforts at a global scale,26 providing consistent, systematic and cloud-free observations with a greater sensitivity to the three-dimensional woody components of mangroves which is good for estimating above-ground biomass and structure.20 Even though other SAR systems provide data that support different mangrove studies, L-band SAR can supply more information for under way monitoring on a global scale.26 Considering the relative scarcity of SAR studies that investigate the structural characteristics of basin and fringe mangroves, the present study aims to evaluate the use of advanced land observing satellite (ALOS) phased array type L-band SAR (PALSAR) data for discriminating distinct physiographic mangrove types with different forest structure developments in a subtropical mangrove forest located in Cananéia on the southern coast of São Paulo, Brazil. The relationships between the different mangrove structural parameters and SAR backscatter values of 10 incoherent attributes using statistical regression models were also evaluated.