This study evaluated the psychometric properties of an on-line version of the Zuckerman-Kuhlman-Aluja Personality Questionnaire (ZKA-PQ) by sex and age. The questionnaire was responded by 1598 people, 474 males and 1124 females, with a mean age of 32.57 (SD = 11.72). Males and females differed in their responses to all personality dimensions evaluated by this instrument, in a similar way as that reported in past research. In addition, younger people scored higher in the Aggressiveness factor, especially concerning the Physical Aggression facet, whereas older people scored higher in the Activity factor. Besides, younger people scored higher in the Neuroticism and the Sensation Seeking factors, even though there were no age differences in the Extraversion factor. The ZKA-PQ five-factor structure was clear and yielded high congruence coefficients with the original Spanish validation sample. Altogether, the findings support the validity of the online version of this instrument. The ZKAPQ online version is therefore helpful in both, basic and applied research settings about human personality and individual differences.