A control box arrangement including at least one control box which has a frame constructed from vertical and horizontal frame pieces and which is fitted with, or can be fitted with, mounting parts including mounting rails, for the variable design of the inside of the control box for the division thereof. The frame pieces have rows of mounting holes in a defined pattern. The division of the inside of the control box can be varied by single-component connection pieces for connecting the mounting rails to the frame pieces. The connection pieces include a coupling section which protrudes at a right angle from the connection plane of the associated frame piece when applied. The coupling section has a quadratic or rectangular cross-section and has at least one transversally extending threaded borehole. The four planes of the coupling section are parallel to the vertical plane and the horizontal plane of the control box.