The present invention relates to compositions and methods for treating diseases and disorders including cancer and various other angiogenic-dependent diseases, vascular malfunctions, arteriovenous malformations (AVM), hemorrhagic processes and treatment of pain, in particular tumor-related pain by drug delivery and/or therapeutic embolization using microspheres. More particularly the invention relates to microspheres containing non-ionic contrast agents, to compositions comprising these microspheres, as well as methods for preparing and using such compositions for embolization therapy. The invention further relates to compositions and methods using detectable microspheres for targeted drug delivery, irrespective of whether embolization is also needed.