An electronic device may include wireless circuitry with first and second receivers. Each receiver may include circuitry for receiving radio-frequency signals using a first radio access technology (RAT) and using second or additional RATs. The wireless circuitry may perform system selection in which the receivers attempt to acquire a signal transmitted by a base station using different RATs. The first receiver and the second receiver may concurrently perform system selection in which the first receiver performs a band scan over the first RAT while the second receiver concurrently performs a band scan over a second or additional RAT. Additional band scans may be performed as needed until a signal is acquired. Once a signal is acquired, the wireless circuitry may establish cellular communications with the wireless base station based on the acquired signal. This may minimize the amount of time required to begin cellular telephone communications in many situations.