In this experimental study, continuous detonation in a small-scale combustor with a chamber diameter of 15.0 mm was investigated using fast-response wall pressure measurements and high-speed flame luminosity imaging. The combustor can be made into an annular geometry by assembling an inner wall with a diameter of 10.0 mm, and a hollow geometry by removing the inner wall. A mixture of ethylene and oxygen was used in the experiments. Continuous detonation waves were successfully established for both combustor geometries. Wave dynamics were studied by changing the equivalence ratio from fuel-lean to fuel-rich conditions. Through the analyses of the wall pressures and the flame luminosity images, two wave modes were identified: the single detonation wave mode and the pulsed wave mode. For most testing cases, the single detonation wave mode dominated the combustion with the pulsed wave mode coexisting as a secondary wave component. For four testing cases using the annular geometry, the pulsed wave mode was dominant while the single detonation wave mode was still present. The change of the wave propagation direction for the single detonation wave mode was observed only for the cases using the annular geometry. The dynamics of the continuous detonation waves in the annular combustor were compared to those in the hollow combustor, showing that faster detonation waves were produced in the hollow combustor. The current experiments demonstrated that continuous detonation can be produced in a small space, resulting in high wave propagating frequencies.