Reflection-absorption IR (RAIR) spectra of sulfur hexafluoride (SF₆) crystalline thin films in 10–100 K temperature range and absorption FTIR spectra of thin layer (90 μm) of liquid SF₆ near the melting point (T_m = 222 K) are recorded. Special attention is paid to combinational bands region. The three types of band behavior upon phase transitions are identified and illustrated by 3ν₆, ν₁+ ν₃, ν₂+ ν₃, ν₁+ν₄ and ν₅+ν₄ bands. The contours of the latter bands uncharacteristically change upon phase transitions. The different behavior of those bands is explained by the various contributions of different band forming mechanisms, evaluated by the mathematical apparatus of spectral moments.