Geometrically frustrated antiferromagnet LuBaCo4O7 exhibits unusual competition between two low-temperature phases with orthorhombic and monoclinic symmetry. Depending on thermal prehistory, this composition can be stabilized in one of these phases or in a mixed state. Magnetic behaviour clearly correlates with the crystal-structure symmetry and is essentially different in both phases. Due to the subtle balance between the competing ground states, the system is expected to be very sensitive for external perturbations such as pressure. Thus, the main aim of the proposed neutron diffraction experiment is to study pressure effect on the structural and magnetic states in LuBaCo4O7.