A Cu target is widely used for X-ray diffraction measurements because it efficiently generates X-rays due to its excellent thermal conductivity and is inexpensive. Additionally, the wavelength of the characteristic line Kα1 allows observation up to a d-value of 0.82 Å (2θ = 140 ̊), so it is suitable for determining crystal structures at atomic position level. Despite these advantages, diffraction profiles for Fe compounds exhibit high backgrounds due to fluorescent X-rays generated by Fe, which makes it difficult to distinguish low-intensity diffraction peaks from the background. Here, we illustrate diffraction results with low background and a high P/B ratio obtained using the X-ray fluorescence reduction mode of a 2D detector with a Cu source.