One-electron systems H₂⁺, H₃⁺⁺, H₄⁺⁺⁺ in strong magnetic field are studied in accurate variational method. For H₂⁺ it is shown that (i) the system exists for all magnetic fields and all orientations, however,(ii) for B > 10¹¹ G system is the most compact for the angle about 45 degrees, (iii) for > 5 10¹¹ G and angles larger than some critical angle the dissociation H₂⁺ -> H + p is allowed. H₃⁺⁺ exists for > 10¹² G as a linear molecule elongated along magnetic line as well as a triangular one perpendicular to magnetic line. A linear configuration is the most stable along one-electron ones for B > 10¹³ G. H₄⁺⁺⁺ can exist for B > 10¹³ G.