Journeys across Bus Éireann, Dublin Bus and Irish Rail fell to 229 million last year, down by almost 3.5 million on 2011, according to the group's annual report for 2012.
The report also shows that passenger revenues increased by €17m last year, up to almost €725m.
However, CIE has described last year as "extremely difficult" financially, with the group recording a deficit of €43.1m which was offset by pension adjustments and a once-off State subvention of €36m.
Chairperson Vivienne Jupp said the company's €492m pension scheme deficit has now become "unsustainable".