The present invention provides compounds of formula (I) and in particular 2-[bis(4-fluorophenyl)methyl]-2,7- diazaspiro[4.5]decan-10-one derivatives and related compounds as inhibitors of human dopamine-active-transporter (DAT) protein for the treatment of sexual dysfunction, affective disorders, anxiety, depression, chronic fatigue, Tourette syndrome, Angelman syndrome, attention deficit disorder (ADD), attention deficit hyperactivity disorder (ADHD), obesity, pain, obsessive-compulsive disorder, movement disorders, CNS disorders, sleep disorders, narcolepsy, conduct disorder, substance abuse (including smoking cessation), eating disorders, and impulse control disorders.