As of the census of 2000, there were 344,765 people, 147,566 households, and 99,016 families residing in the county. The population density was 463 people per square mile (179/km²). There were 173,717 housing units at an average density of 233 per square mile (90/km²). The racial makeup of the county was 93.70% White, 2.07% Black or African American, 0.35% Native American, 0.94% Asian, 0.03% Pacific Islander, 1.52% from other races, and 1.38% from two or more races. 5.69% of the population were Hispanic or Latino of any race.
There were 147,566 households out of which 23.50% had children under the age of 18 living with them, 54.60% were married couples living together, 8.90% had a female householder with no husband present, and 32.90% were non-families. 27.30% of all households were made up of individuals and 15.90% had someone living alone who was 65 years of age or older. The average household size was 2.30 and the average family size was 2.77.
In the county the population was spread out with 20.20% under the age of 18, 5.80% from 18 to 24, 24.10% from 25 to 44, 23.10% from 45 to 64, and 26.80% who were 65 years of age or older. The median age was 45 years. For every 100 females there were 92.20 males. For every 100 females age 18 and over, there were 89.10 males.
The median income for a household in the county was $32,969, and the median income for a family was $39,568. Males had a median income of $30,974 versus $23,802 for females. The per capita income for the county was $18,439. About 7.60% of families and 10.70% of the population were below the poverty line, including 15.20% of those under age 18 and 7.70% of those age 65 or over.
Pasco County Public Transportation provides bus service in West Pasco, Dade City and Zephyrhills.
CSX operates three rail lines within the county. Amtrak formerly provided passenger rail service to Dade City, but the stop was terminated in late 2004.