We present a grand canonical Monte Carlo (GCMC) simulation of argon adsorption in connected cylindrical pores at 87.3 K. A number of pore models are constructed from various components: finite cylinder, finite cone, and flat surface. In the case of two cylinders of different sizes connected to each other with open ends, the adsorption isotherm can be described by a combination of two independent pores, the smaller of which is opened at both ends while the larger one is closed at one end. The adsorption isotherm depends on the relative size between the two sections of the connected pore. In the case of a cavity connected to the bulk surrounding gas via one or two narrower cylindrical necks, the phenomenon of either pore blocking or cavitation is observed, depending on the relative size between the neck and the cavity. If the neck size is smaller than a critical size, D(c), we observe cavitation, while pore blocking is observed when it is greater than D(c). This is due to the dominance of one of two mechanisms for removal of the adsorbates: either the receding of the menisci or the stretching of the fluid in the cavity. We also explore the effects of neck length and cavity length on the adsorption isotherm and conclude that while the neck length has a negligible effect on cavitation, it is of considerable importance when pore blocking occurs, because this process is controlled by the formation and movement of the meniscus in the pore neck. The effect of cavity length is found to be negligible in both cases.