R.A. BORZOOEI AND M. BAKHSHI

In this note by considering the notion of weak hyper BCK-ideal of a hyper BCK-algebra, we study the lattice structure on the class of all weak hyper BCK-ideals. We show that the lattice of these ideals form a Boolean and geometric lattice, under suitable conditions. Finally, we consider the notion of pseudocomplement and we prove that the algebra ( S (I^s_w(H )), &Mac247; V, L) of all pseudocomplements of weak hyper BCK-ideals of a hyper BCK-algebra H is a Boolean lattice.