Let F be a number field unramified at an odd prime p and F_infty be the mathbf {Z}_p-cyclotomic extension of F. Generalizing Kobayashi plus/minus Selmer groups for elliptic curves, Büyükboduk and Lei have defined modified Selmer groups, called signed Selmer groups, for certain non-ordinary {{,mathrm{Gal},}}(overline{F}/F)-representations. In particular, their construction applies to abelian varieties defined over F with good supersingular reduction at primes of F dividing p. Assuming that these Selmer groups are cotorsion mathbf {Z}_p[[{{,mathrm{Gal},}}(F_infty /F)]]-modules, we show that they have no proper sub-mathbf {Z}_p[[{{,mathrm{Gal},}}(F_infty /F)]]-module of finite index. We deduce from this a number of arithmetic applications. On studying the Euler–Poincaré characteristic of these Selmer groups, we obtain an explicit formula on the size of the Bloch–Kato Selmer group attached to these representations. Furthermore, for two such representations that are isomorphic modulo p, we compare the Iwasawa-invariants of their signed Selmer groups.