Lifetime measurement of the first excited 2+ state in 18C was performed using an upgraded recoil shadow method to determine the electric quadrupole transition. The measured mean lifetime is 18.9 ± 0.9 (stat) ± 4.4 (syst) ps, which corresponds to a B(E2
2 1 +→ 0gs + value of 4.3 ± 0.2 ± 1.0 e2fm4, or about 1.5 Weisskopf units. The mean lifetime of the first 2+ state in 16C was remeasured to be about 18 ps, about four times shorter than the value reported previously. By incorporating the γ-ray angular distribution measured in this work into the previous measurement, this discrepancy has been explained. The observed transition strengths in 16,18C are hindered compared to the empirical transition strengths, indicating that the anomalous hindered E2 strength observed in 16C persists in 18C. © 2009 World Scientific Publishing Company.