The image reconstruction in diffuse optical tomography (DOT) is a typical inverse problem; therefore, regularization techniques are essential to obtain a reliable solution. The most general form of regularization is Tikhonov regularization. With any Tikhonov regularized reconstruction algorithm, one of the crucial issues is the selection of the regularization parameter that controls the trade-off between the regularized solution and fidelity to the given sets of data. Automatic methods such as L-curve, generalized cross-validation, minimal residual method, projection error method, and model function method have been introduced to select the regularization parameter over the years. However, little investigation of comparison of all the algorithms has been reported in DOT. The performance of the five methods for choosing regularization parameter is comprehensively compared, and advantages and limitations are discussed.