The present invention relates to tetrahydro-tetrazolo[1,5-a]pyrazine compounds of formula (I), wherein R1 denotes —R3, —CH2—R3 or —CO—R3; R2 denotes Ar2, Hetar2 or C3-7-cycloalkyl; and R3 denotes Ar3, Hetar3 or C3-7-cycloalkyl. These compounds are useful for inhibiting the retinoid-related orphan receptor γ (ROR γ, ROR-gamma) and for the prevention and/or treatment of medical conditions affected by ROR γ activity such as rheumatoid arthritis, multiple sclerosis, psoriasis, ulcerative colitis, asthma, autoimmune hepatitis or type 1 and type 2 diabetes.