Triple X syndrome (47, XXX) is a numerical chromosomal alteration that affects 1/1.000 females, in which the individual is born with an extra X chromosome. Trisomy X is a relatively common but under-recognized chromosomal disorder associated with characteristic cognitive and behavioural features of varying severity. We report a 16-year old patient with Triple X syndrome and resistant schizophrenia. It is remarkable that genetic syndromes may be associated with resistance to treatment of psychiatric problems. Therefore in cases with treatment resistance, the genetic analysis should absolutely be examined.