The present invention relates to a didactic set of pieces for assembling structures, which comprises pieces (1)(2)(3) of optional usage for assembling structures with didactic purposes, comprising compatible assembly pieces (1)(2)(3) and provided with means of reciprocal assembly (4)(5)(16) that, assembled between each other, are able to form structures. It comprises a basic set (1) of pieces (1a)(1b)(1c)(1d)(1e)(1f) which assembly slots (4)(5) are open on any or all the sides (11)(12)(13)(14) comprising the piece perimeter.