Householders in Cork city and county returned the highest number of census forms with a completed time capsule.
The time capsule idea was introduced for the first time in an Irish census last year to offer people an opportunity to write a message for future generations.
The message will be stored securely for a century and will only be released or made available to the public in 2122.
Census 2022 data released on Tuesday shows that nearly a fifth, or 348,443 of the 1.8m households enumerated on census night in April 2022, completed the time capsule section.
The CSO said Cork county and city combined returned the largest number of Census forms with a completed time capsule, at 41,669, followed by Dublin City with 40,857.
The completion rate by county ranged from 16% to 21%, but at 21%, Dún Laoghaire-Rathdown had the highest completion rate followed by Wicklow, Kildare, Mayo and Leitrim (20%).
The time capsules will be stored securely for 100 years in line with Article 35 of the Statistics Act, 1993, after which they will be released to the public.
Another first in last year’s census was a question on voluntary work which showed that 711,379 people reported that they regularly engaged in helping or voluntary work without pay in one or more of five different activities.
Males were most likely to volunteer in a sporting organisation while females were more likely to volunteer in their community.