The relationship is investigated between laminar and turbulent theories of the structure of a collisionless shock wave. For p_e ≫ p_i, where p_i, p_e are the ion and electron pressures, a laminar structure of the shock wave may be constructed in terms of the `solitary' wave with thickness of the order of the Debye length. When p_i ≳ p_e the principal part within the shock front is played by scattering of ions by small-scale field fluctuations which result from anisotropic instability. The thickness of the front is in order of magnitudeΔ ∼ (c/Ω₀)(m_i/m_e)(1/(M-1)²) (M - 1 < 1),where c is the velocity of light, Ω₀ = 4πne²/m_i, m_i, m_e are the ion and electron masses, and M is the Mach number.