The model of an young star with a protoplanetary disk and a low-mass companion ( q \leq 0.1 ) , which is moving on a circular orbit , inclined to the disk plane , is considered .
The hydrodynamic models of such a system were calculated by SPH method .
It was shown the distortions in the disk , caused by the orbital motion of the companion , lead to the strong dependence of illumination conditions of the disk on the azimuth ( because of extinction between the star and the disk surface ) and , therefore , it leads to the appearance of large-scale asymmetry in images of disks .
The calculations showed the dependence of the illumination on the azimuth was stronger in the central part of the disk than on the periphery .
Bright and dark domains are located not symmetry with respect to the line of nodes .
The sizes and locations of the domains are depended on the model parameters as well as on the phase of the orbital period .
The bright and dark domains do not follow the companion , but they make small amplitude oscillations with respect to some direction .
The properties of the model , which were written above , open new opportunities of searching low-mass companions in the vicinity of young stars .
The stars with protoplanetary disks , which are observed face-on or under the small inclination angle i , are the best ones for this purpose .

Key words : protoplanetary disks , hydrodynamics , low-mass companions , noncoplanar orbits .