The aim of this study was to test the potentials of modem analytical methods in the determination of redox properties of constructed wetland. The contents of indivi-dual oxidation states of iron in wastewater samples were determined as an indicator of the redox character of a reed-bed wastewater treatment plant in addition to monitoring their redox potentials. Fe(II) was determined by the 1,10-phenanthroline method, total iron content was determined after reduction of Fe(III) with hydroxylamine hydrochloride. Differential pulse voltammetry served as a comparative method for iron determination. The contents of sulfates, sulfides and dissolved and precipitated manganese species in wastewater samples were also determined. The presence of sulfides in samples documents reducing properties of the wetland system. Fe(III) detected in samples is the result of wetland aeration via the roots of vegetation. The aeration in the presence of redox potential gradients strongly affects the processes of wastewater treatment. The conditions and processes inside the reed bed of a constructed wetland are very difficult to study due to high heterogeneity and complexity of the system. The precise analytical methods used for real samples, with necessary modifications, may afford a tool for studying artificial and natural ecosystems.