The Cathay Pacific Airways website has provided very good write-up on the Cabin Baggage:

For all classes, each passenger (except infants) can enjoy a free baggage allowance of one cabin bag not exceeding 56x36x23cm (22x14x9 in) in size. These dimensions include wheels, handles and side pockets. Different travel classes have different weight limits: First Class - 15kg (33 lbs), Business Class - 10kg (22 lbs), Economy Class - 7kg (15 lbs). *

In addition to the above allowance, you may carry onboard the following items free:
- An overcoat or shawl
- A small handbag
- A briefcase (no more than 4kg or 9lbs in weight)
- A notebook or laptop computer (no more than 4kg or 9lbs in weight, including case and accessories)
- A small camera or a pair of binoculars
- An umbrella / walking stick / crutches
- A "forward facing" infant car safety seat for ticketed child (aged between 6 months and 3 years) or infant bassinet or cot (that can fit on fold down shelves and can be properly secured)
- Infant food and nappies (for consumption in flight)
- An infant collapsible pushchair (if cabin stowage is available)