Elastic properties of a class of two‐dimensional model systems, consisted of hard cyclic multimers, are discussed. Each multimer is composed ofm= 3k(wherekis a positive integer) hard discs of diameter &sgr; and centers forming a perfect polygon ofm‐sides, where the side length isl. Close packed structures of such systems, which are isotropic from the point of view of elastic properties, were solved exactly in the close packing limit at zero temperature. It was shown that the Poisson ratio,vP, of the multimers is negative when their roughness parameter, defined as &agr; ≡l/(2&sgr;), is large. In the limitm→ ∞ one obtains hard disc‐like particles, which in contrast to the standard hard discs arerough. It is conjectured that the formula obtained for the Poisson ratio of the 3k‐multimers,vP= (1 − 2&agr;2)/(3 − 2&agr;2), is valid also form≠ 3kin the limitm→ ∞. © 2004 American Institute of Physics