Plastic film capacitors implement are formed using a metal–plastic film dielectric–metal structure. They are not polarized so they may be connected either to positive or negative voltages.

The internal construction of plastic film capacitors is carried out so that it minimizes the length of current flow, which in turn reduces equivalent series resistance (ESR). All types of plastic film capacitors have relatively low ESR, which reduces losses and heat output. This property enables film capacitors to work in applications with high currents. Plastic film capacitor properties are stable, especially when compared to electrolytic capacitors.

Plastic film capacitors are subdivided into groups based on what plastic film material is used as the dielectric including polystyrene film capacitors, polypropylene film capacitors, polytetrafluoroethylene (PTFE) film capacitors, and others. The type of plastic film determines the characteristics and behavior of the capacitor. Typical behavior of a particular plastic film capacitor type should be investigated before selecting it for use in a given application. For example, the temperature dependencies of comparable capacitors may be different, so a nominally equal plastic film capacitor (but different plastic film material) may exhibit different effective capacitance in the final application.