Preliminary Census results show parts of North, West and South Kerry have experienced population decreases as people moved to urban areas.
Tony Downes of Census publicity says this movement is a nationwide pattern.
However, he says there needs to be further analysis to fully understand the reasons for this.
Census results show there are 687 vacant houses in the Killarney urban area.
While 169 of the vacant properties are holiday homes, this leaves 518 houses classified as vacant.
However, Forensic and Chartered Accountant, Kevin Moynihan, believes the numbers are incorrect and dangerous.
He says the number of vacant homes is considerably smaller, and planners will use the inaccurate figures when trying to address housing issues.
Mr Moynihan says Kerry County Council should get involved and do a study on the number of vacant houses in Killarney.