Oscillatory shear measurements were done on linear poly(oxypropylenediol) and star-shaped poly(oxypropylenetriol) with three arms of equal length. Internal relaxation modes are observed in addition to the local segmental relaxation (alpha-relaxation) for all molar masses investigated between 500 and 8000 g/mol. The alpha-relaxation is well described by a generalized exponential relaxation time distribution in which the parameters have been chosen to give a close correspondence with a stretched exponential decay in the time domain. The corresponding stretched exponent beta = 0.49 +/- 0.01 and is the same for the diol and triol and independent of the molar mass. The temperature dependence of the internal modes is the same for the diol and triol and independent of the molar mass but is weaker than that of the alpha-relaxation close to the glass transition temperature. The shape of the internal modes’ relaxation fits well to the Rouse model, and the molar mass dependence of the slowest relaxation time is stronger than expected from the Rouse model. At a given arm length, taking the linear diol as consisting of two arms, the internal modes of the triol and diol are the same within experimental error. A triol with weight average molar mass 260 g/mol, which corresponds to, on average, less than one POP segment per arm, does not show internal modes and has a significantly broader alpha-relaxation.