Last decade a lot of research was done in the development and investigation of textile-based shielding materials against electromagnetic radiation. Still, there is a gap in understanding the effect of knitted structure (i.e., stitch type and shape) on shielding effectiveness by different shielding mechanisms: reflection and absorption. Seven knitted fabrics were produced on 8-gauge flat knitting machines, using 0.12 mm diameter stainless steel (SS) wire and 30 x 2 tex cotton yarn. The fabrics differ by the method of incorporation of conductive element (SS wire) into the knitted structure: separately and simultaneously with cotton yarn and used interloopings. The effect of stitch type (loop, float, or tuck) was studied as well. It was found that both the method of SS wire incorporation and the shape of its positioning in the knitted structure affect the EMR shielding effectiveness while only the method of SS wire incorporation determines the shielding mechanism: absorption or reflection. The half Milano rib knitted structures demonstrate the best shielding efficiency due to the additional floats behind held loops.