What is the difference between SSD and SSI?

The main difference between Social Security Disability (SSD) and Supplemental Security Income (SSI) is that SSD is available to workers who have attained a specified number of work credits, while SSI is available to those who have not worked or who have not earned enough work credits to qualify for SSD. Also, with SSD, a person’s dependents could potentially receive auxilliary benefit; however, with SSI, only the disabled individual is able to receive any benefits. SSI recipients also can receive Medicaid, while SSD recipients can receive Medicare.