The attacks – late last night – took place in Shantallow and Kylemore Park of Derry.
In Shantallow two windows were smashed in a car parked in Drumleck Gardens and petrol was poured over it.
In Kylemore Park petrol was also poured over a van.
A family was attacked there in 2009.
The PSNI says information can be given to police at Strand Road on the non-emergency number, 101, or by calling the Crimestoppers Charity anonymously on 0800 555 111.