Noninvasive determination of μs' and μa is essential for clinical applications in medical diagnostics and therapeutics. Spatially resolved diffuse reflectance method is more advantageous than other techniques because of its simplicity and low-cost. The methods for solving the nonlinear inverse problem of estimates of μs' and μa from spatially resolved diffuse reflectance Rd(r) can be classified into the algorithms based on absolute or relative reflectance measurements in nature. Since absolute reflectance measurements are technically more difficult to perform than the relative one, study on the methods based on the relative reflectance has a more important meaning for real applications. Considering that there were several normalizations of Rd(r), in this paper we discussed the varieties of prediction rms errors of μs' and μa extracted from relative reflectance data of different normalization forms including Rd(r)/Rd(r)max, r2(Rd(r)/Rd(r)max), 1n(Rd(r)/Rd(r)max) and 1n(r2(Rd(r)/Rd(r)max)). Additionally, we compared the accuracies of μs' and μa determined from absolute reflectance data Rd(r) and 1n(Rd(r)) with that from relative reflectance data to study the loss of accuracy due to normalization. Rather than the traditional neural network methods, we used a new method -- PCA-NN trained with diffuse reflectance data from Monte Carlo simulations to derive μs' and μa. All the PCA-NNs were trained and tested on the space with μs' between 0.1 and 2.0 mm-1 and μa between 0.01 and 0.1 mm-1. The test results indicate that the rms errors in μs' and μa are 0.72% and 2.57% for Rd(r), 0.28% and 0.55% for 1n(Rd(r), 2.98% and 5.44% for Rd(r)/Rd(r)max, 2.22% and 3.21% for 1n(Rd(r)/Rd(r)max), 6.52% and 20.7% for r2(Rd(r)/Rd(r)max), and 2.22% and 3.21% for 1n(r2(Rd(r)/Rd(r)max)), suggesting that the normalization form 1n(Rd(r)/Rd(r)max) would be the first choice for the estimates of μs' and μa from relative reflectance data by PCA-NN. Although the loss of accuracy due to normalization is considerable, the preliminary results provide a guideline for relative reflectance measurements.