Treatment strategies for small side branch compromise related to main vessel stenting are not well investigated and not established.This study is to compare the clinical prognosis of different strategies for bifurcations with or without percutaneous coronary intervention (PCI) of small side branch after it compromised.A total of 119 consecutive bifurcation subjects from January 2013 to March 2015 were enrolled, all bifurcations were characterized by small side branch (1.5 mm ≤side branch diameter ≤2.5 mm). Subjects were assigned into side branch treatment (SBT) group and nonside branch treatment group (NSBT) according to whether advanced treatment of side branch was taken or not after it compromised. Major adverse cardiovascular event (MACE) was evaluated, so were the CCS angina and NYHA heart function classification.SBT subjects were associated with longer procedure time (46.7 vs 19.6 min, P < .001) and more complications (18.9% vs 0.0%, P < .001). 12 MACEs were followed including 4 in SBT group and 8 in NSBT group (10.8% vs 9.8%, P = 1.00). There were no significant difference between 2 groups regarding the CCS and NYHA classification, neither were the calculated classification improvement rate, respectively. In subgroup analysis for true and nontrue bifurcations, no statistical difference was found in terms of the MACE rate, the CCS, and NYHA classification improvement rate.Nontreatment of side branch will not increase the risk of MACE and will not worsen the CCS and NYHA classification when small side branch compromises during the bifurcation PCI.