We performed a cross sectional study to examine the relationship between physical function and mental health of patients waiting for total hip replacement surgery, and the relationship between physical and social function and mental health to time spent waiting for surgery. We found that, in addition to the expected poor hip function, limited mobility and pain, one-quarter of the patients had clinically significant mood disorders and another quarter were in the borderline range. No association was found between severity of mental disorder and assessment of hip function. The patients had been waiting for 1-26 months (median 6 months) for surgery: yet those waiting longest were no worse on any of the outcome measures and their mental health was better. We conclude that mental disorders are common in patients waiting for hip replacements, are not directly related to hip function and their origins are unknown, but they require clinical assessment and treatment. There is no evidence that physical or social function or mental health are worse in those waiting longer for hip replacement surgery. Even so, these patients are severely disabled and some have to wait too long.