A secondary battery pack comprising: a battery cell having an electrode assembly of a cathode/separator/anode structure disposed in a battery case together with an electrolyte in a sealed state, the battery cell having first and second electrode terminals formed at a top thereof; an electrically insulative mounting member having an opening, through which the second electrode terminal of the battery cell is exposed, the electrically insulative mounting member being mounted to a top of the battery cell; a protection circuit module (PCM; 130) comprising a protection circuit board (PCB; 133) loaded on the electrically insulative mounting member, the PCB having a protection circuit, and a connection member (A; 136) and a connection member (B; 132) coupled to a bottom of the PCB, the connection member (A; 136) being connected to the first electrode terminal of the battery cell via a safety element, the connection member (B; 132) being coupled to the second electrode terminal of the battery cell, the PCB being provided with a through hole, through which the connection member (B; 132) is exposed; and an insulative cap coupled to an upper end of the battery cell to surround the electrically insulative mounting member in a state in which the connection members (132, 136) and the protection circuit board are loaded on the insulative cap, wherein a sum of a height of the PCM and a height of the insulative cap is 3.0 mm or less, and characterized in that a receiving sidewall protrudes upward from a top of the insulative mounting member and fastening protrusions (126, 127, 128, 129) are vertically formed at the receiving sidewall such that the PCM assembly is stably mounted to the insulative mounting member. a battery cell having an electrode assembly of a cathode/separator/anode structure disposed in a battery case together with an electrolyte in a sealed state, the battery cell having first and second electrode terminals formed at a top thereof; an electrically insulative mounting member having an opening, through which the second electrode terminal of the battery cell is exposed, the electrically insulative mounting member being mounted to a top of the battery cell; a protection circuit module (PCM; 130) comprising a protection circuit board (PCB; 133) loaded on the electrically insulative mounting member, the PCB having a protection circuit, and a connection member (A; 136) and a connection member (B; 132) coupled to a bottom of the PCB, the connection member (A; 136) being connected to the first electrode terminal of the battery cell via a safety element, the connection member (B; 132) being coupled to the second electrode terminal of the battery cell, the PCB being provided with a through hole, through which the connection member (B; 132) is exposed; and an insulative cap coupled to an upper end of the battery cell to surround the electrically insulative mounting member in a state in which the connection members (132, 136) and the protection circuit board are loaded on the insulative cap, wherein a sum of a height of the PCM and a height of the insulative cap is 3.0 mm or less, and characterized in that a receiving sidewall protrudes upward from a top of the insulative mounting member and fastening protrusions (126, 127, 128, 129) are vertically formed at the receiving sidewall such that the PCM assembly is stably mounted to the insulative mounting member.