l NHS Grampian's report reveals it marked patients as unavailable after informing them they might not be treated within the target time frame – even though the patient was available but had simply agreed to wait longer for treatment.
NHS Grampian say: "No evidence of any kind had been found that Grampian staff manipulated waiting list figures to achieve national targets.
"We would also wish to highlight the arrangements we implement have involved patients in all decisions affecting their pathway of care.
"Thousands of waiting times transactions are carried out every year. Errors do happen but these are genuine and not evidence of systemic failures."
l NHS Tayside's report says a number of staff "spoke of instances of inappropriate behaviour including pressure on them to use unavailability to prevent breaches."
In some instances, staff were "just told to do whatever was required to clear the list".
Out of 367 cases reviewed by NHS Tayside, 25% did not appear to have been handled in line with Government guidance and 17% are described as "causing particular concern".
Examples from NHS Tayside include patients being marked as unavailable "simply to avoid a month end breach" and, as in Grampian, patients being marked unavailable because they had been told treatment could not be delivered on time.
l In a sample of 297 records checked, NHS Lanarkshire found 17% of transactions were not in line with guidance. They note that "on occasion written offers (of appointments) were being sent to patients two or three days prior to appointment date." They also say "periods of unavailability were added retrospectively up to 138 days after the period of unavailability started."
However the board says their view is these issues were to do with misunderstandings and not manipulation.
l NHS Highland says in the sample of cases it tested there were a small number of issues, including a patient who had been marked unavailable for 26 days "apparently without sufficient justification".
The board noted that when staff suspended patients from waiting lists, they often did not record details about why they had done so. This occurred in around a third of the test cases.