A multifunctional cross-bridged tetraaza macrocyclic compound has at least one side arm that comprises a moiety that is capable of forming a bond with another molecule, which has a targeting moiety that directs the compound to a site a marker substance. The compound is chelated to a medically active material that generates a signal for diagnostic imaging or produces a therapeutic effect at the site of the marker substance. A method for detecting, diagnosing, and/or treating a disease that produces the marker substance uses a conjugate comprising the multifunctional cross-bridged tetraaza macrocyclic compound.