Double Sided Silicon Strip Detectors (DSSSDs) are segmented silicon detectors widely used for the detection of charged particles. When a particle hits the inter-strip gap between two adjacent strips, energy measurement can be affected by different effects reducing the efficiency of output signal generation. With the purpose to study this behaviour, an experiment was performed at the scanning proton micro-beam facility of the Ruđer Bošković Institute (RBI). Response of two detectors of thickness 75 and 998 µm is examined as a function of the beam impact position and bias voltage. Results show that the effective width of the inter-strip gap, which is linked to the efficiency for full energy detection, depends on the experimental conditions and detector settings.