A pixel arrangement structure, an organic electroluminescent display panel, a display device, and a mask assembly. The pixel arrangement structure comprises: a plurality of first sub-pixels (01) in positions that do not overlap with each other, a plurality of second sub-pixels (02), and a plurality of third sub-pixels (03). One of the plurality of first sub-pixels (01) is located at a center position of a first virtual rectangle and four of the plurality of first sub-pixels (01) are respectively located at four vertex positions of the first virtual rectangle. Four of the plurality of second sub-pixels (02) are respectively located at four side center positions of the first virtual rectangle. The first virtual rectangle is divided into four second virtual rectangles, and each of the interiors of the four second virtual rectangles comprises a third sub-pixel (03) of the plurality of third sub-pixels (03).