  Lorentz-invariant mass and mean propagation velocity have been found for
structured light pulses in vacuum considered as relativistic objects. We solved
the boundary problem for such widely known field configurations as Gauss,
Laguerre-Gauss, Bessel-Gauss, Hermite-Gauss, and Airy-Gauss ones. The pulses
were taken having the finite duration temporal envelope. We discovered that
Lorentz-invariant mass and mean propagation velocity significantly depend on
the spatial-temporal structure of pulses. We found that mean propagation
velocity is independent of the full energy of the pulse and is smaller than the
speed of light.
