A pyrazolopyrazine compound of the following formula (I). ##STR1##

wherein

R¹ is hydrogen or a suitable substituent; and

R² is hydrogen or halogen,

or a salt thereof.

The pyrazolopyrazine compound (I) and salt thereof of the present invention are adenosine antagonists and are useful for the prevention and/or treatment of depression, dementia (e.g. Alzheimer's disease, cerebrovascular dementia, dementia accompanying Parkinson's disease, etc.), Parkinson's disease, anxiety, pain, cerebrovascular disease (e.g. stroke, etc.), heart failure and the like.