[en] The magnetic properties of orthorhombic Ho_1-xY_xNi compounds have been studied from resistivity, magnetization and neutron diffraction experiments. The Curie temperatures decrease linearly from 37.5 K in HoNi to 4 K for Ho_0.2Y_0.8Ni, while Ho_0.1Y_0.9Ni and YNi do not present any magnetic long-range order. Below T_C the compounds show a non-collinear magnetic structure belonging to a single irreducible representation, which evolves at lower temperatures towards another non-collinear structure described by the mixture of two irreducible representations. The appearance of both magnetic arrangements is discussed, comparing these structures with those of other rare earth nickel compounds and taking into account both crystalline electric field and exchange interactions. (author)